The actual process of repairing or changing the IMEI using Z3X involves:

Before starting, you must understand three key elements:

Launch (Ensure it is updated to the latest version supporting U8 security patches).

Boot the phone into Download Mode, connect it via USB, and click .

Go to Settings > About Phone > Software Information > Build Number . Look for the 5th character from the right. It must be 8 (e.g., G930FXX S8 ERJC or G930FXX U8 ERG2). You cannot downgrade a U8 device to U7 or lower firmware.