Be aware that it can take just a few seconds, or several hours to take root. The first time I did it I thought it had frozen, so I did a battery pull and reran it. I left it sit while I watched a movie (had checked on it after about an hour and 20 minutes had passed and was still spinning), and at the end of the movie it had rebooted and was rooted.
After accidentally updating my phone again I had to reroot with Z4 again. This time it took all of 15 seconds tops and it was rerooted (it might be worth mentioning that I did a battery pull just before that one as well). Make sure you are in debugging mode.