http://laws.flrules.org/files/Ch_2005-027.pdf there it is.
776.013 Home protection; use of deadly force; presumption of fear of
death or great bodily harm.
(1) A person is presumed to have held a reasonable fear of imminent peril
of death or great bodily harm to himself or herself or another when using
defensive force that is intended or likely to cause death or great bodily harm
to another if:
(a) The person against whom the defensive force was used was in the
process of unlawfully and forcefully entering, or had unlawfully and forcibly
entered, a dwelling, residence, or occupied vehicle, or if that person had
removed or was attempting to remove another against that persons will
from the dwelling, residence, or occupied vehicle; and
(b) The person who uses defensive force knew or had reason to believe
that an unlawful and forcible entry or unlawful and forcible act was occurring
or had occurred.
Under part 1, zimmerman has no protection
(2) The presumption set forth in subsection (1) does not apply if:
(a) The person against whom the defensive force is used has the right to
be in or is a lawful resident of the dwelling, residence, or vehicle, such as
an owner, lessee, or titleholder, and there is not an injunction for protection
from domestic violence or a written pretrial supervision order of no contact
against that person; or
(b) The person or persons sought to be removed is a child or grandchild,
or is otherwise in the lawful custody or under the lawful guardianship of,
the person against whom the defensive force is used; or
(c) The person who uses defensive force is engaged in an unlawful activity
or is using the dwelling, residence, or occupied vehicle to further an
unlawful activity; or
(d) The person against whom the defensive force is used is a law enforcement
officer, as defined in s. 943.10(14), who enters or attempts to enter a
dwelling, residence, or vehicle in the performance of his or her official duties
and the officer identified himself or herself in accordance with any applicable
law or the person using force knew or reasonably should have known that
the person entering or attempting to enter was a law enforcement officer.
Section 2 does not allow for defensive force to have been used in this situation
(3) A person who is not engaged in an unlawful activity and who is
attacked in any other place where he or she has a right to be has no duty
to retreat and has the right to stand his or her ground and meet force with
force, including deadly force if he or she reasonably believes it is necessary
to do so to prevent death or great bodily harm to himself or herself or another
or to prevent the commission of a forcible felony.
Section 3 does not apply to zimmerman either.
The law does not protect what he did at all.