This is a big plus in that the prosecution will have to bring out every shred of evidence it has at this early hearing in an attempt to rebut the assertion of self-defense. If it has nothing, Zim will walk. If it has something then the defense gets an early opportunity to cross examine the state witnesses and "lock them in" with regard to any later testimony at trial. It is going to be very, very difficult to convict this guy.
Which is why he was not arrested originally.
As Dershowitz has already harped on, prosecution was already required to bring out all objective evidence (regardless of which side it benefits). There isn’t any. Short of late-breaking discoveries, introducing anything now that was withheld then will go very badly for the prosecution.