Follw the link below:
[TUTORIAL] Change region/ID to International in Meizu Pro 5
AND most important thing is the version of SuperSu and BusyBox.
Click there to down Tools APKs  password: fpww
Flyme OS 5.1.3.0A 稳定版 （暨新春特别版）...
Flyme OS 5.1.3.0A
Download Inernational firmware from flymeos.com
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If you did it .Congratulations.BUT some PROBLEM there:
You can't use the service of China Telecom .(It not important)
I were asked to login a strange account in Meizu Accont.(I can login easily in "A" firmware. )

Finally , hope it helps ,
AND if you know how to solve this problem. PLEASE tell me.