Stock Firmware ZTE Trek 2

Versions available :
K88V2.0.0B17, B15 = Nougat.
K88V1.0.0B31, B33 = Marshmallow.

Downloads:
Google Drive
Mediafire
Mega
4Shared

the version K88V2.0.0B17 and K88V2.0.0B15 should extract update.zip and pass it in micro sd or use pc method adb sideload

K88 SD Card Upgrade Instructions
Or pc using adb sideload (Firmware file)

Example:

1: enter recovery and select adb sideload, from your ZTE Trek 2

2: on the PC opens the command window and writes adb sideload (file name)

example: adb sideload update.zip