My brother opened a new forum dedicated to Zenit (and related), yet it lacks visitors, so if you have a question, something to tell... enjoy it! it is at zenit.forumparfait.com.For my part, I suggest you entrust me with your Zenit to repair or service (there are also other old mechanical cameras I know) so do not hesitate to ask (via my professional website).
That, it's for the anecdote: birth of the Forum, and launch of my repair business. It was a quasi-voluntary, it is now completely voluntary (except for possible spare parts, and return shipping). The professional website is closed, repairs are now on this site!