Without benefit of all the evidence. If I had to hazard a guess right now, I would think Zimmerman is at worst guilty of Man 2. If the jury's only option's are either convict Murder 2 or acquit, I would say Zimmerman gets a walk, or at least based on what's evidence has been made available to date you'd have to lean that way.
Now common sense would say they would have the option to convict on the lesser charge. But this is Florida after all, and if I'm not mistaken the Casey Anthony jury didn't have that option, and that's why she's free today. So I'm not sure what would be different in this case that they'd have the choice?
If by chance it's murder 2 or nothing the D.A did a terrible job in filing this case regardless of verdict. .