ZTE USB Modem not working in Yosemite
I found a solution from web and it works on my ZTE-MF667 with no problem.


Go to System Preferences → Network
If you see your USB connection on the left side go to step 5.
If not, select the "+" icon like this.


Select your Interface and set your Service Name like this, then select Create:


Select ZTEUSBModem and set Configuration-Default, Telephone Number: #99*

Account Name and Password must be blank.Then select Advanced


Set Vendor: Generic and Model: GPRS(GSM/3G)


Click OK and Connect.