Comments here:
http://www.hlntv.com/video/2012/03/21/floridas-stand-your-ground-law-under-fire
...would seem to be saying that if SYG applies, Zimmerman has immunity, but if police don’t file charges, or if he is merely found by a jury to have acted in “self-defense,” then he MAY be sued civilly.
I don’t vouch for the accuracy of these things, just offering something for your consideration. IANAL (and stuff like this is why!)
Also, they can sue the police, and will very likely be encouraged to do so.
776.032 Immunity from criminal prosecution and civil action for justifiable use of force.--Florida Statutes - Chapter 776(1) A person who uses force as permitted in s. 776.012, s. 776.013, or s. 776.031 is justified in using such force and is immune from criminal prosecution and civil action for the use of such force, unless [the person is a police officer, lots of stuff snipped]
So, if there is a finding that the use of force was justified (self defense is a justification), he's immune from both criminal and civil proceedings.
If there is a finding, by a jury, then he never had the immunity on the first place. That is, finding by a jury means there was a criminal prosecution (or a civil one - but here we are talking about whether or not the civil one can go ahead)
I just read that article. I agree with it. Take some time and read it slowly, it is exploring several different branches of possible outcome, and how they are reached.