In order to hard reset a ZTE Rio II, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
ZTE Rio II device will be brought back to the default configuration of a brand new device.
1. Switch on the device by pressing the Power button.
2. Now open the Dialer and enter this code in: *983*22387#
3. Lastly, confirm the process by selecting Yes.