My Z has started to develop rattles from the hatch area. Like the plastic pieces are shaking loose but this only happens in the drone zone under heavy throttle 3500-4500rpm. I am pretty sure its the louder after market HFC and Exhaust it never did it in stock from.
To the OP definitely get your Z to the dealer its under warranty they may be able to find the issue and fix it.
Also I found a tread that may help with the rattles:
Rear Hatch is Rattling