In order to hard reset a ZTE A206, you should perform the following steps.

Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
ZTE A206 device will be brought back to the default configuration of a brand new device.

1. Turn the phone off, then turn it back on.

2. Enter an emergency dial and type this code into it: *983*22387#
3. Select the Erase Everything option. Done.