I don't know anything about the Zorki, but the Leningrad is a bit quirky. If you can find a good, working one, it has some interesting characteristics. The viewfinder is very bright and clear by '50s FSU standards, and the split-image-only rangefinder works well as long as the subject has clear vertical edges on which to focus. The black framelines for lenses from 50mm through 135mm are even "semi-compensated" for parallax (the image moves horizontally but not vertically as you focus.)
On the downside, one big irritant is that a lot of non-FSU lenses won't fit; the camera mount is a standard L-39 thread, all right, but there's a decorative ridge just above it that physically interferes if you try to screw in a lens that's too fat around the base. When I had a Leningrad, I was annoyed to discover that none of my Canon or Voigtlander lenses would fit.
The other thing that's a bit of a headache is that the sprocketless film-advance system produces uneven frame spacing. At the beginning of a roll the frames almost touch each other, but by the end of a 36-exposure roll the spacing is about twice the normal amount. This isn't a big problem if you process and cut your own negatives, but it drives automatic printing and slide-mounting equipment crazy.
So -- fun camera if you get a working one, and a very interesting design -- but if you're contemplating it for a "user," think hard about whether these limitations would be a problem before you dive in.