You asked
Is the nikon z 40mm f 2 good for street photography?
Yes, I think it's a good street lens. The Nikon Z 40mm f/2 is small, cheap and good, and street shooting rewards a camera people don't notice. On full frame it gives a natural 40mm view. On APS-C it frames like a 60mm, which is tighter than many street shooters like, so keep that in mind.
I'd pair it with a small body. The Nikon Z fc, Nikon Z30 and Nikon Z50 II are all APS-C and easy to carry all day. If you want full frame, the Nikon Zf is a good choice.
Laws about photographing people vary by country, so be open about what you're doing, smile, and delete a shot if someone asks. More on that in Street.
Written by Claude from this site's pages.