[ZTE Axon 7 Questions & Answers] runninghamster:
Hey man, glad that you asked before doing anything more. There's never anything wrong with asking for help. First things first, if you're trying to install the Axon 7 Drivers on your PC, these are actually the Qualcomm EDL Drivers. You can find these very simply by googling for 'qualcomm edl drivers' and then clicking either the first or second link. Install these, and after that you will want to install the ADB drivers. I assume you already have these, and know how to use ADB as per implying in your post. I'll still link them if you need them.

- After installing both drivers, reboot your PC and connect your phone to the PC. Enable USB Debugging and OEM Unlocking from Developer Options on the phone.

- Since you have already extracted the Axon 7 EDL Tool to the base of your C:/ drive (should be C:/Axon 7 EDL Tool), simply launch it by right-clicking the .bat file inside the folder and running it as administrator. The tool will show up, and you will see a warning. Press Y and agree to it, and your phone will automatically be switched off and put into EDL mode.

- At the top you will see 'Device connected!' in green. Now you can select the option 'Unlock' and then 'Bootloader Unlock'. Follow the steps on screen, and then you should have an unlocked bootloader. You can tell it's unlocked because it will show up everytime you start your device; "Your bootloader is unlocked".

- That was basically the hard part. Now you can simply just download a TWRP image, I would recommend this one. Download it, and rename it to 'recovery.img'. Place it in C:\Axon7_EDL_Tool\flash\recovery folder. Open up the EDL Tool again (make sure device is connected to computer and shows up as "Connected!" at the top of the tool), and select 'Flash' and then 'Recovery'. It will flash the TWRP image you downloaded.

- Once finished, you can reboot to your system on your phone, and download the latest LOS 15 .zip (your choice between Official builds or Unofficial), the Universal Bootloader, your device's modem (Flash depending on your phone model, here's A2017U and here's A2017G), and Opengapps to access the playstore. Make sure to download ARM 64 8.1 gapps. You can pick whichever size package you want, I would recommend Micro or smaller.

- Once downloaded, move all your stuff to your phone, and reboot to your TWRP (Volume Up + Power Button). Select Wipe, and slide the toggle at the bottom. Then go back and select Wipe again, but this time select Advanced and Wipe everything except your Internal storage. Now you can go into Flash, and flash in this order: Universal bootloader, modem, los15 zip, gapps. Simply reboot to system, and you're good to go. PS If you end up getting an error when you flash the los 15 zip, ignore it and flash the zip again.

IF you want to try some other Oreo rom, you can find plenty on the forums and even try a GSI. For the most stable, I recommend trying out LiquidRemix which is 9.0 Pie, OmniROM, which is also Pie, or DotOS/crDroid/ViperOS which are Oreo and you can find on our forums. You do not need to flash a vendor with DotOS/crDroid/ViperOS because they already come with one. Just follow the steps in each respective thread. There is no VoLTE, Wifi Calling and the camera flash is not synced on any rom that isn't LOS or Stock. You'll need to wipe all your partitions except Internal and External Storage, and then flash a vendor (Use either NFound vendor, Kranoner vendor, or the LOS Vendor. Each vendor has it own differences, but essentially do the same thing. LOS Vendor will be the fastest out of all 3, but does not work on some roms/gsi (will not boot). After flashing your vendor, flash your system.img and then flash your gapps. Now you can reboot.