https://forum.xda-developers.com/xperia-xz/how-to/how-to-unlock-bl-kernel-twrp-root-t3541648
ow, if you want to restore your TA partition and relock your Bootloader this is absolutely simple.
First of all, backup all the data you care of. Because your phone will be factory reset. Take your backuped TA partition and rename it TAbackup.img
Then, start your phone into recovery mode (TWRP)
Plug your phone with USB and check your device is recognized in recovery mode : adb devices
If it's okay, let's run this command now : adb push TAbackup.img /data/local/tmp/TAbackup.img
Then run this one : adb shell dd if=/data/local/tmp/TAbackup.img of=/dev/block/bootdevice/by-name/TA
Well, your TA partition is now back. Plug your phone off and you just have to flash a new STOCK ROM via FlashTool.
Now you have your original DRM and your bootloader is automatically relock !
Flash the stock ROM you want with Flashtool and enjoy a fresh and clean install