Firstly ,if you need any data , backup after do this.
Step by step system install guide
1-Download and extract Optus_V9_Upgrade_30th_April_patched.zip file
2-Open Sales_MultiDL_MSM7227_patched.exe(if yo have "fail to find 'RecordCSV.sdi',please select setup folder[or other errors].skip,this not important error)
3-Hold volume down and power key.After you see FTM on screen unhold buttons.
4-İnstall driverinstaller.exe and connect your ZTE to computer with usb cable.
5-Find device com port(use device manager).example
6-Select firmware folder.Example
7-And click start all button :
8-Now your ZTE okkk.
Important note if you insert sim card and your device need network lock code use this site and calculate unlock code:
All thanks to Gsmhosting forum