In order to hard reset a ZTE Grand Memo V9815, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
ZTE Grand Memo V9815 device will be brought back to the default configuration of a brand new device.
1. Take out the phone's battery, then put it back in.
2. Press'n'hold the Volume Up, Volume Down and Power buttons simultaneously.
3. Press Home button when the Android logo pops on-screen.
4. Using Volume Down button to scroll and Power button to confirm, select the wipe data/factory reset option.
5. Continue by selecting Yes - delete all user data and reboot sytem now.