I attached the Nikon Z7 with my Nikkor 400mm f/2.8 ED FL and the Nikkor 600mm f/4 ED FL lenses to for compatibility using very big pro FX glass.
The links for the performance with these cameras are below.
First challenge is the The Nikon Z7 and Z6 camera is so light it is impossible to balance the camera and super telephoto lens without adding rear counter balance, the system remains front heavy. Good news is the camera has two bottom attachment for adding weight - you need to be creative or add a small bag with optional weights. The FTZ adapter allows a bottom adapter and the other is at the camera adapter, so get creative if the front balance is a problem.
Adding a 1.4 TC makes the situation a little better but still is front heavy and frustrating to use without a proper rear balance.
For my wildlife setup, I use the Wimberly Gimbal Head with a Gitzo Series Three Carbon Tripod. However, using the 600mm I feel a series 4 or even 5 tripod would be more appropriate.