According to Droid Life, the Moto Z's first update is rolling out. Sounds like it's mainly security patches. I checked on my Zf, and it didn't see the update as available yet.
http://www.droid-life.com/2016/08/29/moto-z-droid-finally-getting-first-update/
The updates are arriving as build MCL24.246-36 and weigh in at about 436MB.
As for what’s new, well, they don’t really say much other than they provide “enhancements, improvements and the latest Android security updates.” Of course, “latest” isn’t really correct in the security department since this update only provides the July security patch. Keep in mind that we are almost in September, so within days this phone will already be two months behind in patches.
http://www.droid-life.com/2016/08/29/moto-z-droid-finally-getting-first-update/