Hard Reset ZTE Nubia Z7 Max

First method:

1. Power on the phone.
   
2. Then scroll to main screen, and press Menu button.
   
3. Next select Privacy -> Factory data reset.
4. After that read the disclaimer, then press Reset.
5. Choose Erase everything.
6. Afterwards your phone will reboots.

Second method:

1. Switch off your cell phone.
   
2. Afterwards press and hold together Volume Down + Power button or Volume Up + Power button.
   
3. Now you should to press Menu button to enter the Recovery Mode, when you see triangle with Android green man.
   
4. Then form the menu choose option "Wipe Data/Factory Reset" using Volume Down to browse option, and Power button to confirm.
5. After that select "yes" -> use Volume buttons to scroll to, and Power button to enter.
6. In the end press Power button to accept option "reboot system now".

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