[ZTE Axon 7 Guides, News, & Discussion] Darkcrafter3@gmail.com:
Quick notes:

ALL files/software needed are linked below

Process only confirmed working for this model, A2017U

Desktop PC used is on Windows 10 x64, no 3rd Party Antivirus

I assume you have ADB installed on your computer, but if not here is an easy guide:

https://xdaforums.com/showthread.php?p=48915118#post48915118

Also assumed you have the Axon7 connected to PC via USB cable

Here's the steps I took, with info compiled and reorganized from the two guides linked at bottom of post:

1. The downgrade from B15 Nougat to B29 Marshmallow

(skip to step 2 if you are already on B29)​

A- Download the full B29 software package, provided by ZTE on their website. Select the support tab halfway down the page, then select the software updates to download the .ZIP (mirror provided at bottom in case ZTE changes things)

B- Download it, unzip it once, then put the update.zip file on your SD card.

C- Turn on OEM unlocking in the Axon Settings Menu (it is needed to flash from sd card)

You can do this by navigating to Settings -> About phone -> Tap "Build number" 7 times.

Now navigate to Settings -> Advanced settings -> Developer options -> Enable "OEM unlocking".

D- Boot phone to recovery - [Power] + [Volume Up] key combo - Release the keys when you see the ZTE logo.

E- Choose update from sd card, then pick the update.zip from the sdcard

F- The phone will flash the B29 software. It is a bit slow, have patience and let it do what it needs to do.

2. Unlocking Bootloader and installing TWRP​

A- Install the Qualcomm QUSB_BULK drivers. You should be able to simply extract them, then right click qcser.inf and press Install.

B- Boot the Axon7 into EDL mode. [Power] + [Volume Up] + [Volume Down]

C- Your device should be recognized in Windows’ Device Manager as a COM port called "Qualcomm HS-USB QDLoader 9008".

D- Download and Unzip the FASTBOOT_UNLOCK EDL file.

E- Install MiFlash on your computer. Open the program.

F- In MiFlash, Select the folder "A2017U_FASTBOOT_UNLOCK_EDL". Use the child folder inside containing fastboot.img and other files. Do not use the parent folder containing the META-INF folder, it caused flashing to fail for me.

G- Now just hit [flash] - watch the progress bars move and wait for the device row to turn green with flash complete!

H- Use [Power] + [Volume Up] key combo to exit EDL mode and enter recovery

I- Open CMD window as admin, and use "fastboot oem unlock" command to unlock (and wipe) your device. When prompted on Axon7, select Yes to unlock bootloader

J- Reboot phone into EDL mode

K- Return to MiFlash, Select the folder "A2017U_B29_TWRP_EDL". Click [refresh] if device row shows anything under status.

L- Now just hit [flash] like before - watch the progress bars move and wait for the device row to turn green with flash complete!

M-Reboot phone to TWRP

If the flash fails or is unable to communicate with the device, use the [Power] + [Volume Up] + [Volume Down] key combo to restart EDL mode.

Release the keys after 5 seconds then wait another 5 seconds before using the [refresh] or [flash] buttons on MiFlash.

3. Installing Lineage OS With Root​

A- Using TWRP, Wipe the device (data/cache/dalvik, all that stuff)

B- Install the Universal Bootloader (A2017X_B15_Universal_Bootloader.zip), and modem (A2017U_N_Modem.zip)

C- Install Lineage OS ROM .zip, with root addon (addonsu-arm64-signed.zip)

D- Install Gapps

E- Restart Axon7, enjoy!

Thanks to the reply made by u/tabletalker7 on my last thread, I now have an unlocked bootloader, TWRP, and LineageOS with root. 10/10 !

DOWNLOADS:​

Official ZTE B29 Marshmallow Software Package:

ZTE Website

Gdrive Mirror

Qualcomm QUSB_BULK Drivers: (WHQL certified)

Click here to download

FASTBOOT_UNLOCK EDL Package:

Click here to download

TWRP for A2017U EDL Package:

Click here to download

Universal Bootloader and Modem packages for A2017U:

Click here to download

Lineage Official Builds:

Click here to download

Lineage OS root addon:

Click here to download

Open GApps: (arm64) (use 7.1 if using Lineage 14.1)

Click here to download

CREDITS:​

[OFFICIAL] LineageOS 14.1 for ZTE Axon 7 by Unjustified Dev:

https://xdaforums.com/axon-7/development/unofficial-lineageos-14-1-zte-axon-7-t3545679

[EDL][A2017/A2017U] Emergency DL Mode TWRP + Unlock + Upgrade By jcadduono:

https://xdaforums.com/axon-7/development/edl-emergency-dl-mode-twrp-unlock-t3553514