Seems like a problem not being able to extract files from a downloaded firmware ZIP file. I won't dig into that - but here's a copy of the readme.

============ MONTAGE6/MONTAGE7/MONTAGE8 V1.50 Operating System Updater Readme ============

Thank you for purchasing the Yamaha MONTAGE Series, Music Synthesizer.

This Readme file contains important information about the MONTAGE6/MONTAGE7/MONTAGE8 V1.50 Operating System update and the updating process.
Please read this document carefully before updating your MONTAGE synthesizer.

NOTICE:
- This updater is only for the MONTAGE synthesizer.
- This updater is to be used at the user's own risk.
- All User memory (Library data, User data, User sample and so on) will be initialized by this updater. Please make sure that you have saved all User data to a USB flash drive before performing this update.
- The unit may become inoperable if the electrical supply is interrupted while running the updater (by disconnecting the AC cord, etc.). If this happens, run the updater again from the first step.
- If the unit does not function after running the updater, please contact your nearest Yamaha service center.

Yamaha Global Gateway
https://www.yamaha.com/countries/

This update is applicable to the following version:
MONTAGE6/MONTAGE7/MONTAGE8 with firmware versions earlier than V1.50

How to check the version of your MONTAGE

1. Press the [UTILITY] button to open the Utility display.
2. Touch [Setting] tab -> [System] tab at the left side of the display.
3. The following message appears in the bottom of the display:
@@@--------------------------------------------------------------------------
@@@@MONTAGE Firmware Version : *.**.* (c)2016 Yamaha Corporation
@@@--------------------------------------------------------------------------
The unit's version is indicated by " MONTAGE Firmware Version : *.**.* "
Only the numbers up to the two decimal places after the first dot are important in reading the version number, you can ignore the numbers after the second dot.
Ex.) 1.02.0 =1.02 , 1.10.0= 1.10

Updating Procedure

NOTICE:
All User memory (Library data, User data, User sample and so on) will be initialized by this updater.
Please make sure that you save all User data to a USB flash drive before performing this update.
Library data cannot be backed up. Please prepare the original library data.
In addition, when you load backup data, load libraries first before the user data.

Required Items
- One USB flash drive of over 1GB capacity formatted on the MONTAGE

1. After downloading, copy the following uncompressed files to a USB flash drive that has been formatted on the MONTAGE. No other files should be present on the USB flash drive.
8N70OS_.PGM

2. Power off the MONTAGE.

3. Connect the USB flash drive prepared in step 1 to the [USB TO DEVICE] terminal of the MONTAGE. Power on the MONTAGE while holding down the [Cursor UP] and [UTILITY] buttons until the "YAMAHA" logo appears on screen.

4. The MONTAGE OS updater will begin with the message "Searching for the updater..." and "MONTAGE updater *.**.*".
When the message "Finish. Please turn off." appears, turn off the MONTAGE and remove the USB flash drive.

WARNING:
DO NOT power off or remove the USB flash drive from the MONTAGE until the "Finish. Please turn off." message appears. If power is accidently interrupted while running the updater (by disconnecting the AC cord, etc.), the unit may become inoperable. If this happens, run the updater again. If the unit still does not function after doing this, please contact your nearest Yamaha service center.

5. Power on the MONTAGE.

This completes the update process.

=======================================================================================================================
Fixes and Enhancements

New features;
- New effect types have been added.
- New Performances have been added.
- The Favorite function has been added.
- gMixingh has been added for the gParameter with Parth setting of the Part Category Search.
- From the Performance Play (Home) display, you can now see various information.
- The Super Knob Link function has been added.
- You can now control the monitor volume of the Audio signal input from the [USB TO HOST] terminal.
- You can now switch Scenes by Control Change messages.
- You can now make partial changes to the font size on the Live Set display and the Category Search display.
- You can now save/load backup files in which the entire User Memory data (including Songs and Libraries) is stored.
- Each Edit display has been improved by allowing touch selection of Parts from the display.
- Improved the sensitivity of Audio Beat Sync.
- Improved the visibility of the selected Performance in the Live Set display.
- MOXF6/MOXF8 data (X6A, X6V, X6G, and X6W) can now be loaded to MONTAGE.
- Enhanced the Note Shift control from the panel (holding down the [SHIFT] button and using the OCTAVE [-]/[+] buttons to change the transpose value in semitones), so that once you change the value, you can release your finger from the [SHIFT] button and continue to make semitone changes for a short time by using only the OCTAVE [-]/[+] buttons.

Fixed problems;
- Fixed a problem in which an error message would appear when Device Number was set to other than "All" and a Super Knob Control Change message was received.
- Fixed a problem in which Zone settings would not be correctly applied by switching Performances.
- Fixed other minor problems.

New features;
- Switching time between Performances has been reduced.
- Element / Operator Control has been added for gControl Function.h
- You can now store Control Function settings as Performance data.
- Song Loop playback function has been added.
- User Arpeggio function has been added.
- You can now separately mute original Parts and newly added Parts by Performance Merge.
- Monitor Volume settings for USB connection have been added.
- You can now control the Super Knob by MIDI Control Change messages.
- You can now copy or exchange Arpeggio Types.
- You can now copy or exchange Motion Sequences.
- You can now copy or exchange Live Sets in different Banks on a page basis.
- The MONTAGE Connect computer application is now supported.
- MOTIF XS data (X0A, X0V, X0G, and X0W) can now be loaded to MONTAGE.
- You can now switch Performances from the Live Set display during Audio playback.
- Knob Brightness setting can now be stored.
- Flags (tone generation attributes of Performance) can now be automatically set and displayed.
- Arp Bypass and Kbd Ctrl Lock functions have been added for gEffect Switch.h
- Pedal fuctions such as sustain and sostenuto have been improved to reproduce realistic acoustic piano sound.

Fixed problems;
- Fixed a problem in which all buttons, sliders, and knobs on the panel would not work after power-on.
- Fixed a problem in which the Super knob would not work after power-on.
- Fixed other minor problems.

Fixed problems;
- Improved the sensitivity of performance response.
- Fixed a problem in which this instrument would freeze if you set Lane of the Motion Sequencer to "Arp" before starting MIDI recording.
- Fixed a problem in which this instrument would freeze when reading certain Standard MIDI File data.

New features;
- New Performances have been added.
- From the Performance Play (Home) display, you can now view Part types and categories of each Part.
- From the Performance Play (Home) and the Mixing displays, you can now turn the Arpeggio Hold function on/off.
- In the Part Category Search, you can now specify any Part other than Part 1 as the Part to be copied.
- Performance Merge function has been added.
- MIDI single channel mode has been added.
- From the Data Utility display (in the Utility display) you can now delete multiple contents together.
- You can now copy Performances from the Library memory to the User memory.
- You can now copy or exchange Elements/Operators/Drum Keys.
- You can now copy or exchange Live Sets on a Bank or page basis.
- Live Set pages and slots can now be controlled by MIDI Bank Select and Program Change messages.
- In the Live Set display, you can also register a Live Set by pressing the [SHIFT] and [LIVE SET] buttons simultaneously.
- When you press the OCTAVE [+] or [-] button to change the octave or transpose setting, a pop-up display with the current value appears.
- When you press the [SHIFT] and KNOB POSITION [1] or [2] buttons simultaneously to memorize the positions of knobs, a pop-up display appears.
- "All" was added to the value of the display filter of the Control Assign display.
- You can now change the cursor position in the text input with the right and left cursor buttons.

Fixed problems;
- Fixed the problem in which a user waveform would be lost when loading libraries exceeding the sample memory size.
- Fixed the problem of long load times when loading large samples.
- Fixed the error in saving a Song as a MIDI file when the Song name contained illegal characters.
- Fixed other minor problems.

=======================================================================================================================
The company names and product names in this release note are the trademarks or registered trademarks of their respective companies.
Copyright(c) 2016 Yamaha Corporation. All Rights Reserved.

Have not been able extract the readme file. Other than the same update instructions as before is there anything else important?

Yes, you will need to backup your data. Any installed Libraries will be purged. So assemble the files you used to install them because you will need to reinstall your Library data.

Backup any data you currently have in your USER Bank.
Make sure you have .MID files for all your SONGs