While holding it, via USB cable.
The Xperia Z3 D6633 will now restart. The first boot after a hard reset takes significantly longer than usual (sometimes up to 5-10 minutes) as the system rebuilds the cache and sets up default apps. Do not panic; this is normal. How to Hard Reset SONY Xperia Z3 D6633
Ensure your Xperia Z3 D6633 has at least . If the phone dies during the reset, it could corrupt the firmware, potentially bricking the device. While holding it, via USB cable
If your phone is functional and you can navigate the menus, this is the safest and easiest method. Open Settings : Access the app from your home screen or app drawer. Navigate to Backup & Reset : Scroll down and select Backup & Reset Initiate Reset Factory Data Reset Confirm Erasing Reset Phone Erase Everything to confirm. Do not panic; this is normal