The ZI I had for almost three years was very happily mated to a Voigtlander Heliar Black 50mm, f2 M mount version. It never let me down. But good luck finding one.
Nikkormat FTN, FT2, Nikon F, Nikon D7000
Lots of Nikkor Glass
Pentax MX - SMC Pentax-M 50mm 1.4