These are the instructions to root ZTE Grand Memo N5 v9815 (running on android 4.1.2) using Framaroot Application on Phone itself (does not require computer).
Requirements: Your ZTE Grand Memo N5 v9815 smartphone should have at-least 10-20 percent of phone battery to perform the rooting process.
Optional: You can also verify the root status of your device by using the Root Checker Application.
[*] No data loss process: Your ZTE Grand Memo N5 v9815 Phone Data like contacts, pictures, videos, music and etc will be not affected with the above method.
[*] Device Warranty: Once you full unroot your device through SuperSU, you can claim for the phone warranty. In short no need to worry for phone warranty.
[*] How to unroot: To unroot, Open SuperSU > Settings > Full Unroot.
[*] ZTE Stock Firmware: If you are looking for the original firmware for your device, then head over to Download ZTE Stock Firmware for all devices page.
[*] ZTE USB Driver: If you are looking for the original USB Driver for your device, then head over to Download ZTE USB Driver page.
[*] Credits: Framaroot Application is developed by alephzain (XDA Developer).