Unless it is proven that Zimmerman had a “depraved mind” I don’t see how he can be convicted of murder. The state hasn’t proven a “depraved mind”. I don’t see manslaughter either. It appears to be a justifiable use of force, having your head pounded on concrete can cause “great bodily harm” or death.
http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Display_Index&Title_Request=XLVI#TitleXLVI
Fla. Stat. § 782.04(2) Murder.— The unlawful killing of a human being, when perpetrated by any act imminently dangerous to another and evincing a depraved mind regardless of human life, although without any premeditated design to effect the death of any particular individual, is murder in the second degree and constitutes a felony of the first degree, punishable by imprisonment for a term of years not exceeding life or as provided in s. 775.082, s. 775.083, or s. 775.084.
Fla. Stat. § 782.03 Excusable homicide.—Homicide is excusable when committed by accident and misfortune in doing any lawful act by lawful means with usual ordinary caution, and without any unlawful intent, or by accident and misfortune in the heat of passion, upon any sudden and sufficient provocation, or upon a sudden combat, without any dangerous weapon being used and not done in a cruel or unusual manner.
Fla. Stat. § 782.07(1) Manslaughter.- The killing of a human being by the act, procurement, or culpable negligence of another, without lawful justification according to the provisions of chapter 776 and in cases in which such killing shall not be excusable homicide or murder, according to the provisions of this chapter, is manslaughter, a felony of the second degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084.
Fla. Stat. § 776.012 Use of force in defense of person.—A person is justified in using force, except deadly force, against another when and to the extent that the person reasonably believes that such conduct is necessary to defend himself or herself or another against the other’s imminent use of unlawful force. However, 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 or another or to prevent the imminent commission of a forcible felony; or
(2) Under those circumstances permitted pursuant to s. 776.013