Download Asus X008 ZC520TL official stock rom from the link below and follow the instructions after download link to learn how to flash.
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: Asus_X008_ZC520TL_MT6737_20170316_6.0.zip
Size: 1 GB
Android version: 6.0
Firmware Link: Download
How to flash
After downloading the Flashtool firmware, follow the instructions here to flash.