You can't unlock the bootloader, and cwm can only be used via fastboot. There is already a guide for it.

 

http://androidforums.com/volt-all-things-root/874943-so-you-upgraded-z4-lost-root-guide.html

thats the "guide" to fix root if you already updated and lost/cant root i wrote. i use the term guide very loosely. If you just take out the downgrading part then you have the how to root and unmask fastboot and boot into cwm guide.