“Would Zimmerman give up his right to defend his life if he threw the first punch, started losing the scuffle, and ended up in a life threatening situation with his brains being splattered on the sidewalk?”
He would give up his legal claim of self-defense.
That will (likely) be the prosecution’s contention; ie. that Zimmerman initiated the conflict.
Further they will contend the police dispatcher advised him to not pursue. And the prosecution will establish Captain of Neighborhood Watch carries no police power or authority.
Prediction: Jury convicts on manslaughter of some kind (if that is how it works in Florida).
But there are a lot of variables to get there, including skill of lawyers on both sides, jury selection, evidence and handling thereof, etc.
Maybe Zimmerman can get Shapiro to defend him?
And the defense can claim the dispatcher advised him TO pursue. Prior to the "we don't need you to do that", the dispatcher twice says "Just tell me if he does anything else". A few seconds later Martin "runs", and Zimmerman follows, before being called off.