"Immunity from criminal prosecution and civil action for justifiable use of force" is Florida Statutes 776.032. It, 776.012, and 776.041, are all part of Chapter 776, which is "Justifiable Use of Force." Much, but not all, of that Chapter, came from the Stand Your Ground Act of 2005.
Florida Statutes 776.041 is titled "Use of force by aggressor" and isn't going to be the relevant statute unless Zimmerman was the aggressor. If he wasn't, then Florida Statutes 776.012 stands on its own.
If Zimmerman was not the aggressor, F.S. 776.012(1) states:
[A] a person is justified in the use of deadly force and does not have a duty to retreat if: (1) He or she reasonably believes that such force is necessary to prevent imminent death or great bodily harm to himself or herself[.]
If the party claiming justifiable use of force was the aggressor, then Florida Statutes 776.041(2) ("Use of force by aggressor') is relevant:
The justification described in the preceding sections of this chapter [776] is not available to a person who: . . .(2) Initially provokes the use of force against himself or herself, unless:
(a) Such force is so great that the person reasonably believes that he or she is in imminent danger of death or great bodily harm and that he or she has exhausted every reasonable means to escape such danger other than the use of force which is likely to cause death or great bodily harm to the assailant; or
(b) In good faith, the person withdraws from physical contact with the assailant and indicates clearly to the assailant that he or she desires to withdraw and terminate the use of force, but the assailant continues or resumes the use of force.
Mayo:
A concussion is a traumatic brain injury that alters the way your brain functions. Effects are usually temporary, but can include problems with headache, concentration, memory, judgment, balance and coordination