You asked
Is the nikon z 24 50mm f 4 6 3 good for portraits?
Here is what the site says about that.
From Nikon Z 24-50mm f/4-6.3: Nikon Z 24-50mm f/4-6.3: A zoom lens by Nikon for Full frame cameras, 24-50mm f/4-6.3. A very compact kit zoom for the full-frame bodies. Specs - Maker: Nikon - Focal length: 24-50mm (zoom) - Maximum aperture: f/4-6.3 (it gets darker as you zoom in) - Made for: Full frame sensors - Mounts: Nikon Z - Stabilised: no - Autofocus: yes What it frames like - On full frame (Nikon Z): as marked, 24-50mm. - ...
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.