In an episode aaagees yang lalu Zack's in prison for multiple murders (asssisting a serial killer) what happens in the end??

I'm assuming you're alluding to the big reveal, where Zack tells Sweets that he didn't actually kill anyone. But he swears Sweets to secrecy, because he's still an accomplice, and since he's of sound mind, they would transfer him to prison, where Hodges previously assured Zack that he wouldn't survive. (Zack is currently in a mental hospital/facility for criminals, not a "real" prison.)

OR, anda might be talking about how the case ended, in which case-- the mother killed her son because he was learning to become independent.

(Season 4, Episode 4, "The Perfect Pieces in the Purple Pond.")