I was playing around with 4.3 all last night and managed to get root on my Z with locked BL,
Here is how I did it..
(Locked bootloader, skip unlocking if already unlocked)
- Flash the .67 firmware via flashtool
- Root 4.2 as you would have
- Unlock your bootloader and Backup the TA partition to relock this without losing any DRM keys
- Using flashtool flash the new firmware .569 (4.3)
- Then flash Doomlords advanced stock kernel
- Boot 4.3 and power down
- Using the recover installed with the kernel flash a superSU.zip from somewhere around here.
- Reboot and you now should have root
- Reflash ONLY just .569 kernel from the FTF
- Power on and Restore your TA partition to relock your boot loader and return everything back to normal..but with some root
As for your bootloader not unlocking properly i would first check to see if an unlock is allowed