You asked
What is the nikon z 14 30mm f 4 s good for?
Here is what the site says about that.
From Nikon Z 14-30mm f/4 S: Nikon Z 14-30mm f/4 S: A zoom lens by Nikon for Full frame cameras, 14-30mm f/4. Specs - Maker: Nikon - Focal length: 14-30mm (zoom) - Maximum aperture: f/4 - Made for: Full frame sensors - Mounts: Nikon Z - Stabilised: no - Autofocus: yes What it frames like - On full frame (Nikon Z): as marked, 14-30mm. - On APS-C (Nikon Z): like 21-45mm on full frame; f/4 gives about the depth of field ...
From Focal length converter: How it works: Multiply the focal length by the sensor's crop factor to get its full-frame equivalent. To go between two smaller formats, multiply by the first crop factor and divide by the second. Crop factors are measured on the sensor diagonal, so formats with a different shape (4:3 against 3:2) frame slightly differently across the width.
Quoted from this site's pages.