First of all make sure your device can be unlocked or not, To Check Follow the steps below :
In your device, open the dialer and enter *#*#7378423#*#* to access the service menu.
Tap Service info > Configuration > Rooting Status. If Bootloader unlock allowed says Yes, then you can continue to the next step. If it says No, or if the status is missing, your device cannot be unlocked.
Now Go to the official Unlock Bootloader website of Sony: CLICK HERE.
Scroll down and select your device, and press Continue.
Now register your email.
You will receive a mail to confirm, Tap on “Click here to proceed”.
Once you enter into the Sony Unlocker page, you will be asked to enter your smartphone IMEI no, Now ENTER THE IMEI NO inside the BOX.
You will get your unlock key once, Now Copy the unlocker key in a notepad.
Now You need to enable the Developer Option on your phone.
To Enable the Developer Option. – Go to your Settings -> About Phone -> Now Tap on the Build Number 7-8 Times until you see a toast message “Developer option enabled“
Now go to Developer option in the settings and Enable OEM unlock.
Download ADB Fastboot tool and Extract the ADB Fastboot Tool somewhere in PC (Link is given above)
Now Open the Extractor ADB and Fastboot folder and Open Command Window by pressing Shift Key + Right Mouse Click.
Now connect the PC to Mobile with USB Cable
You need to Reboot the phone into Bootloader – Type the Command from below in your Command window that you openedadb reboot bootloader
Your device will boot into bootloader. (If it doesn’t then please check your Cable or ADB Drivers and Install again). Now enter the command with your unlock key after the OEM unlock and replace this character 0x07B7BFEA7AC879F0 with your unlock keyfastboot -i 0x0fce oem unlock 0x07B7BFEA7AC879F0
That’s it! You have successfully Unlock The Bootloader On Sony Xperia XZ2.