You asked
Best telephoto lens for nikon z?
I don't have a telephoto lens for Nikon Z on the site yet, so I won't name a pick. The Nikon Z lenses I do cover are primes, and none of them is a telephoto: the Nikon Z 40mm f/2 is a small, cheap everyday prime, and the Nikon Z 50mm f/1.4 and Nikon Z 35mm f/1.4 are fast standard-to-wide primes.
For telephoto, I'd start with the focal length guide. It puts 200mm and beyond in the telephoto range, which is what you want for wildlife and sport. If that's your subject, the wildlife and sport page covers how to choose. Then browse the gear catalogue for the Nikon Z telephoto options I haven't written up yet.
Written by Claude from this site's pages.