I've never owned a Zenit but several acquaintances did, and were happy with the purchase from a value for money point of view.
I've got a Quarz 8mm cine camera inherited from my grandfather which was made at the KMZ factory, I believe the same one where Zenit cameras originated from. It's a bit agricultural, and probably was 10 years out of date in the West when it was launched....but it still works nearly 60 years later, still functions exactly as it did when my grandad bought it second hand in 1966.
If you got a decent example, those Russian cameras represented great value. However, as people say, fresh out of the factory not every example was well made.