The Zorki 4 is one of the better Soviet rangefinders. It's a little heftier than the Zorki 1 and FED 1 (copies of the Leica II), but not overly large. Unlike those earlier models it has a removeable back for film loading, slow shutter speeds, a self-timer, and diopter adjustment. And the Zorki 4 usually comes with a faster f/2.0 Jupiter 8 lens, which is a very good to excellent performer. Older Zorki 4's have a vulcanite body covering, but the majority have a nylon fabric covering (servicible, but not very pretty). Zorki 4K's have a rapid film wind lever, which some people prefer. But the numbers on the 4K's shutter speed dial are painted on rather than engraved as on the Zorki 4, and can wear off with use (some people apply clear nail polish over the Zorki 4K's shutter speed dial to protect the painted numbers).
There is a lot of information on the Zorki 4 on the internet - do a Google search and you find lots of sites that discuss this camera. In my opinion, it is a very useable rangefinder that usually sells for prices that are below its true value. But shop around and try to find one that is in good condition.