One thing to keep in mind though is that the 42mm has faster rate of fire (I think by at least 2 sec shortened, but no hard numbers on that one).
This bumps the DPS up quite a bit and makes it an okay-ish unit against everything it can somewhat reliably penetrate.
Even including the faster RoF, against target it can still pen 100% of the time, it still has lower DPS then ZiS.
It has high "fear factor" tho, because you see a lot of shells coming your way and it makes you back up in situations, where you could just drive straight and circle M-42.