[ZTE Axon Pro] suunnittelija:
I was able to install Chinese ZTE Axon Elite (A2015) Marshmallow rom to my international version of Axon Elite (A2016). Wifi, mobile data network and calling works. All Google apps are working too, Chinese rom has google services installed but those are needed to be activated by allowing them run in a background. Only Chinese and English languages available, but system is working in your local language after installing More Locale 2 from Google Play.

This ROM is not rooted, so you need to install Super User in TWRP right after installing this ROM.

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Changes:

Added modem files (modem.b00-modem.b22, modem.mdt) from international B06 NON-HLOS.bin.

Minor build.prop changes (e.g. changed English as default language).

Removed stock recovery.

Added Google Play, Google Contact sync, Google Calendar sync, Google Gmail, Google Exchange sync, Google Phone, More Locale 2.

Removed all possible Chinese ZTE bloatware (over 200MB). I had to leave Mi-Assistant so that it can be used for allowing apps running in a background (example Google Play, Super SU).

[*]Added stock Marshmallow boot animation and removed boot sound.

Features:

Latest Google Security patch

MiFavor UI 4.0 with new themes and fonts

Applications Avatar (I have no idea what it is)

Toolbox - including compass, noise test, ruler, protractor, level meter, paintings

Calendar, shows weather for five next days

New Desktop backup and recovery capabilities

Long screenshots

More system Sleep functions

Smoother UI animations

SMS two-finger zoom

New power limits

Enhanced ZTE lock screen

...and some more which might not be useful in other countries than China (please check more details from: http://www.myzte.cn/thread-270646-1-1.html)

Working:

Wifi, mobile network, mobile data, bluetooth.

Fingerprint scanning.

Google Play services + other Google apps are working too (like Calendar, Contacts sync), but must be activated in Mi-Assistant Auto-start manager and allowing permissions in apps. Please see attached images for example.

Bugs and limitations:

NFC doesn't work.

Only Chinese and English languages, but it is possible to use More Locale 2 app (included in ROM) to change locale settings. Then apps (and part of the system) are working on your defined language. On my opinion it works just like in B06. More Locale requires Root access and executing ADB command (app shows the needed command) to change locale.

Download (B15M beta, updated 09.09.2016):

Mega https://mega.nz/#!cRAXTbqQ!UYTEzWb4AH5yZbcI4fK_09QBM5TYgvCCMMl1uTijetE

Based on the tip from [MENTION=3272619]martas.vavra[/MENTION], I removed stock Chinese recovery so TWRP is not deleted after installing this rom.

Working Super user can be downloaded here https://cloud.tapatalk.com/s/57550023717f4/SuperSU_V2.62-3.zip. Thanks again [MENTION=3272619]martas.vavra[/MENTION].

Quick steps:

(optional) Backup all apps by using ZTE own backup/restore app. It's then possible to restore apps after rom installation.

Install TWRP+root by using the method by [MENTION=264630]acer73[/MENTION]: http://xdaforums.com/zte-axon/development/zte-axon-elite-a2016-twrp-root-t3237760

Copy ZTE_Axon_Elite_A2016_unofficial_B15M_09092016 to SD card.

Boot to TWRP recovery.

Do full backup in TWRP.

Do factory reset in TWRP.

Install ZTE_Axon_Elite_A2016_unofficial_B15M_09092016 from SD card in TWRP. NOTE! Status bar is not progressing at all when installation is ongoing! Don't panic. Just wait, it will complete.

Install Super User .zip again.

Reboot. Please be patient, first boot will take minutes to complete.

After first boot is complete, start Mi-Assistant and enable apps (Google Play, Google Contacts, SuperSU... etc) in Auto-run Manager.

Enable app permissions for Calendar, Contacts, Phone, SMS, Storage in Settings -> Apps, App permissions.

Reboot.

(optional) Restore apps by using ZTE own backup/restore app. ZTE has removed Backup/restore app but here's download link for backup/restore app from B12M: https://mega.nz/#!hZQ2HTbb!IvTJu17kjibXGSJBsRUutz0wwPZL0XlruDVAyExqsC8

Note to users: I'm not responsible if you brick your phone, so please be careful!