For some ZTE modems, the command is:
AT+ZUNLOCK=<code>
But you need the code. Without it, you can try brute-force, but that’s impractical.
Alternatively, try:
AT+ZNLOCK=0
If modem accepts it, it disables network lock.
Or: unlock modem zte m26z1z
AT+ZNCK=0
Then reboot.
In most modern ZTE M26Z1Z, these commands are disabled in firmware. Method 3 rarely works unless you find a specific firmware exploit for your exact firmware version. But you need the code
Advanced users can unlock the ZTE M26Z1Z for free by sending AT commands via a terminal program (like Putty or HyperTerminal). Proceed with extreme caution; incorrect commands can brick the modem.
Yes, in most countries.
Advantage: Works even if carrier refuses to give code. Disadvantage: costs a few euros.