To reset a ZTE phone, you can follow these steps:

1. Switch off your device.
2. Press and hold Volume up and Power button together for few seconds.
3. As soon as the ZTE logo appears, release both the buttons.
4. Next, press and hold Volume up and Power button together again immediately as you see Android Robot pop up.
5. Now, you will be able to see a Menu from where you have to choose “Wipe Data/Factory Reset”.

Alternatively, you can also reset your ZTE phone via Settings App:

1. Go to the Settings menu.
2. Scroll down to tap on the System option and tap the "Advanced" feature to display advanced options.
3. From the drop-down options, select "Reset Options".
4. Tap on "Erase all data (factory reset)" to completely reset the ZTE phone.