[ZTE Axon 7 Guides, News, & Discussion] spiwar:
Note: You can try this with EU ROMs but I'm not sure if it will work, and won't be testing to see if it works, since I see no reason to flash EU ROMs anyways.

I knew this from day 1, but was switching between various LOS ROMs so didn't have much inspiration to make a guide. Now i'm switching back to Stock-based ROMs (due to other roms having no dolby, no voice capture,...), I'll be making a guide

I'm not responsible for bricked device.

This is a guide for those who are facing issues when trying to flash US, EU stock and stock-based ROMs on the chinese axon 7 (no signal, no wifi, worse battery, or simply not booting after splash screen). Since downgrading is also a part of this guide, I will also be covering how to downgrade Nougat 7.1.1 ROMs back to 6.0.1 Marshmallow.

Important thing to note:

You must be on B13, 6.0.1 marshmallow with stock recovery, and please, DO NOT UPDATE TO B10 China NOUGAT or anything above ! This will cause a lot of problem, as from what I've deduced, US B19 is based on the China B09 update, anything above B10 won't be backwards compatible. and will cause problems like not booting, (or no wifi, signal etc after you recover the boot partition through recovery)

Now, if you're already on Nougat and want to try this guide, downgrade back to Marshmallow using EDL. Try this guide:

- Download B13 EDL (credits to djkuz from 4pda), extract it

- Download and install the latest Xiaomi MiFlash (stable or beta)

- Turn off your phone, plug it in to your PC, Hold Power + Vol Up + Vol Down, go to device manager, look for the "Port" section, and you will see something like Qualcomm HS-USB QDLoader 9008., if you see it, proceed down below. If not try again.

- right click , open properties on the Qualcomm HS-USB QDLoader 9008, go to port settings, if you see the speed is at 9600 bits per second (bps), change it to 128000 (you can skip this step, but doing it will increase your flashing speed)

- Open MiFlash, press select and pick the folder you extracted a few steps ago.

- Press refresh, if you see your device appearing on the list, press flash. (if some random errors appear, unplug the device, plug it back and immediately press refresh and press flash)

- After flashing you'll be back on B13 China Marshmallow.

REMEMBER, DON'T OTA UPDATE IF YOU WANT A SMOOTH TRANSITION TO US ROMS:

Now, to the good part:

- Download the B09 China OTA package from here (credits to Demons-77)

- put the package into your EXTERNAL sd card, internal won't do.

- reboot to recovery (Power + Vol Up)

- select the option with the word "sd" on it

- now go and pick the package that you just put in

- It will begin flashing and after that, you will have B09 China Nougat

- reboot to bootloader and install recovery (fastboot flash recovery *your file name*)

- after that you can install any roms you like, no need to backup and restore the boot partition every time you flash a US ROM, and you won't encounter strange issues like no boot, no wifi, etc.

TL;DR for those who already know how to do most of these: go back to China Marshmallow through EDL, update to B09 China Nougat with stock recovery, install TWRP and then flash whatever US stock or stock-based roms you want (just like how you would with a US phone)