[ZTE Axon 7 ROMs, Kernels, Recoveries, & Other Deve] mwiley:
[MENTION=5513820]killacam1989[/MENTION] [MENTION=5971371]RoyBM[/MENTION]

Got my ZTE A2017U yesterday. It was on 7.1.1 Nougat B25. I got it all setup after a little experimentation and thought I'd share.

Based on my experience, I think you should be good to go. First, a summary the steps I think will get you setup...

Use MiFlash to flash B19-NOUGAT_FULL (Nougat 7.1.1). When that's done, you'll be able to boot B19. When it boots, run `adb reboot bootloader`. When bootloader's up, run `fastboot oem unlock`. Confirm it's unlocked by re-booting into bootloader and it should say "DEVICE STATE - unlocked" at the bottom of the bootloader screen. Next, boot back into EDL and flash B19-NOUGAT_TWRP (Nougat 7.1.1). This broke my system (i.e. I couldn't boot into B19 anymore), but it got me TWRP that I then used to install my ROM (AICP in my case) and gapps. Once finished, I'm up and running rooted, unlocked, and happy. One note, when the phone first boots it complains "your device software can't be checked for corruption" and encourages you to re-lock the bootloader. While I had no system, it would hang at this message. After flashing AICP, the message goes away after 5s as it says it will.

Here's a more detailed break-down of my process. I hit a couple hang-ups, but maybe they'll help if you find yourself in a similar situation...

1) I had previously installed the drivers from the installer that mounts when you plug in a stock phone and choose the "install drivers" option on the phone, so I uninstalled those.

2) from the OP, I installed Xiaomi MiFlash and Qualcomm QUSB_BULK Drivers

3) Opened MiFlash

4) booted into EDL as the OP instructs (hold Volume Up + Volume Down + Power until you're stuck on a black screen). This took about 5s of holding the buttons, then I saw a very quick LED flash and my windows device list flashed and showed that there was a new COM device (Qualcomm HS-USB QDLoader 9008 as described by the OP)

5) Clicked the Refresh button in MiFlash and saw my device listed

6) Used the select button in MiFlash to select the FASTBOOT_UNLOCK files (A2017U_FASTBOOT_UNLOCK_EDL directory)

7) Clicked flash and watched it until it completed successfully

8) Rebooted the phone

9) At this point I was expecting that I could run 'fastboot oem unlock', so I ran 'adb reboot bootloader' from windows and the phone rebooted

10) Instead of booting into bootloader, the phone booted as normal (I should have just flashed B19-NOUGAT_FULL)

11) Not knowing what was going on, I again got into EDL and flashed B19-NOUGAT_TWRP thinking maybe I'd get lucky and could just run TWRP

12) Rebooted into recovery, only this time there was no recovery, it booted straight into the system (i.e. despite me holding vol up + power, normal boot occurred)

13) Obviously I did not get lucky, so I took others' tips to heart that B25 can't be unlocked and that I needed to downgrade to B19

14) Back to EDL, flashed B19-NOUGAT_FULL

15) When finished, I rebooted and let it boot and verified in "Settings -> About phone" that I was on B19

16) Tried `adb reboot bootloader` and succeeded this time

17) Once the phone had loaded bootloader, 'fastboot oem unlock' -- success

18) EDL again, flashed B19-NOUGAT_TWRP

19) On normal boot, It would hang at the "your device software can't be checked for corruption" screen, but booting into recovery loaded TWRP!

20) Used TWRP to flash my ROM and gapps

21) success :)

Hope this helps. Definitely worth the effort.