The prosecution can keep saying isn’t this possible, and isn’t that possible, but that can never equal proof beyond a reasonable doubt.
Maybe Zimmmerman was winning, maybe he was on top, maybe he wasn’t afraid for his life - but none of that is the same as proving something that actually happened to the jury.
The prosecution needs to be able to tell the jury “We KNOW it happened THIS way because of x, y, z.”
Exactly! The prosecution needs to prove, beyond a reasonable doubt, that Zimmerman committed Second Degree Murder.