I'll probably open up a can of worms with this, but, those on *UNLOCKED* phones can use my UNIVERSAL script in the House of Moto to flash older FXZ's. It will skip the TZ partition. Why you'd WANT to do this is beyond me. If you're unlocked, you don't need an "exploitable" version to acquire root, for example. You just need custom recovery and a supersu zip.
Those who are LOCKED can skip this post as it does NOT apply to you.