To factory reset your ZTE phone, you can follow these steps:

1. Press and hold the Power and Volume up buttons until the device vibrates and the ZTE logo appears.
2. Release the Power button but continue to hold the Volume Up button until the 'Android Recovery' menu appears.
3. Select Wipe data/factory reset.
4. Or, go to the Settings menu and tap on System > Advanced > Reset Options > Erase all data (factory reset).
5. Confirm your choice and wait for the reset to complete.