You asked

Is the nikon z 28 400mm f 4 8 vr good for portraits?

Here is what the site says about that.

From Nikon Z 28-400mm f/4-8 VR: Nikon Z 28-400mm f/4-8 VR: A zoom lens by Nikon for Full frame cameras, 28-400mm f/4-8. A 14x travel superzoom for full frame. Specs - Maker: Nikon - Focal length: 28-400mm (zoom) - Maximum aperture: f/4-8 (it gets darker as you zoom in) - Made for: Full frame sensors - Mounts: Nikon Z - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Nikon Z): as marked, 28-400mm. - On APS-C ...

From Lenses: Your first lenses: 1. A standard zoom, 24-70mm or 24-105mm equivalent. The kit zoom is fine to start. 2. A fast standard prime, a 50mm f/1.8 on full frame or a 33-35mm f/1.4 to f/1.8 on APS-C. Low light, people, food. 3. Then add for what you shoot: a telephoto zoom for wildlife and sport (wildlife and sport), a wide zoom for landscapes (landscape), or an 85mm for portraits (portraits).

Quoted from this site's pages.

From these pages