Download ZTE Maven 2 (Z831) official firmware update from the link here, and follow the provided flashing instructions to learn how to flash the stock rom.
If you notice that any of the links provided below is broken or doesn’t work, please post in comments section so we fix and update it ASAP.
File Name: ZTE_MMB29M_Z831_6_0_1.rar
Size: 922 MB
Firmware – Download
How to flash
Click here to view complete flashing instructions for any of the above firmware packages. If you have any issue with flashing, post in comments section below for assistance.