You must have the Xperia XZ Premium Drivers installed on your PC. Step 1: Download Official FTF Firmware
To get a and safe firmware file, it is highly recommended to use XperiFirm , which downloads official files directly from Sony's servers. You must have the Xperia XZ Premium Drivers
Flashing a stock ROM will erase all user data , including photos, contacts, and apps. You must have the Xperia XZ Premium Drivers