Hard Reset ZTE Blade S6 Plus

First method:

1. First of all turn off the device by holding the Power rocker.
2. Then press and hold Volume Up + Power button for a couple of seconds.
3. You can release held keys when you see an Andoid image.
4. Choose "wipe data/factory reset" by using Volume buttons to navigate and Power button to confirm.
5. Select "Yes--delete all user data". Use Volume Down button to scroll and Power key to select.
6. To restart the phone, select "reboot system now".
7. Success! The hard reset has just been performed.

Second method:

1. Turn on the phone by using the Power button. 
2. After pressing the Home button go to Settings and then to Backup & reset.
3. Choose the Factory Data Reset.
4. In the next step tap Reset Phone. 
5. Select Erase Everything if you are sure you want to clear all your data. 
6. Well done!

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