I have rooted my Z1 stock 14.4.A.0.108 with Flashtool 0.9.18.1 (the latest one is 0.9.18.2) without problems. Only I needed to reinstall BusyBox after the root process.

Well, because my Z1 can't reboot into recovery after the "standard" process, I installed recovery following the next steps

- Copy Z1-lockeddualrecovery2.7.154-BETA.flashable.zip to the SD Card
- Backup TA (with v9.11). You must backup your TA partition if you're planning to use custom ROMs or unlock the Bootloader in the future.
- Flash recovery with Z1-lockeddualrecovery2.7.154-BETA.installer.zip. To do that, just uncompress the zip archive and execute install.bat
- If everything is OK the Z1 reboot into recovery.
- At this step I needed to reflash the recovery from SD Card using Z1-lockeddualrecovery2.7.154-BETA.flashable.zip (Why? I don't know, but as I said, my Z1 can't reboot into revovery without the second flash from SD)
- After the "second flash" I rebooted my Z1 and everything is working like a charm.
- Now I can reboot into any recovery using NDR Utils

I hope this helps.