Folow the steps in the video and it will work just fine i just unlocked my xperia z3 android 6.01
https://developer.sonymobile.com/unlockbootloader/
ps:
For the imei of the phone you can log in in to the guest user of the phone open the diler and tap *#06#
Also you need to unlock developer mode you do that using the same guest acount go to setings-about phone-build number and click on that 7 times
The proces will erase all the user data on the phone so be sure to back up your data