Download ZTE Blade A521 official firmware from the link here, and follow the offered flashing guidelines to find out how to flash the stock ROM.
If you notice that any of the links provided below is broken or does not work, please post in comments section so we repair and upgrade it ASAP.
|337160 B0565 ENT_CL_BA521 _ V4.0
|339110 B0613 CLA_CO_A521 _ V1.1
How to flash ZTE Blade A521 firmware
Click here to view complete flashing instructions for any of the above firmware packages. If you have any problem with flashing, post in comments area below for help.