One of the best offline method in unlocking any zte modem is using the DC unlocking client (DC CRAP).
the unlocking can be achieve by follow the highlighted steps bellow :

step 1: Download dc crap here
step 2: Extract the file
step 3: Run the dccrap as administrator












step 4: change the manufacturer to ZTE DATA CARD
step 5: change the model tab to Auto detect
step 6: press the find key (hand lens image)
step 7: click on the unlocking tab


Then wait for the successful message remove the modem from the laptop insert any sim then you are good to go.

NOTE: Make sure you put an unsupported sim card before taking the steps to unlock the modem and also remember to install the modem on the pc.