Hard Reset ZTE Blade IV

First method:

1. First please remove SIM card from the phone.
2. Next power on the phone.
   
3. Then press "Emergency call" and dial / type this code: *983*987#

Second method:

1. Make sure, that your phone is off.
2. Now press and hold this buttons: Volume Down + Volume Up + Power key.
   
3. Next from the menu choose "Wipe Data/Factory Reset", using Volume buttons to scroll to option, and Power button, to confirm operation.
4. Then select "yes", and confirm with Power button.
5. After that press Power button to enter option "reboot system now".
   

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.