There are many smartphones with 13Mega pixel back camera. 16MP camera Android phone is less. ZTE Z9 MINI NX511J is one of them.
here is the third-party recovery from YDSS.
link:http://pan.baidu.com/s/1i4tbb8L Password: 3wqe
please follow “install-recovery.bat” to install steps by step,then your z9 mini will restart to recovery mode automatically.Or You can choose press volume+ and power key at the same after power off to recovery mode.Now you can root or backup your z9 mini