It's called ASSAULT. It's illegal. If you walk up to a person and the you sucker punch them in mid sentence, then beat their head on the curb without any apparent provocation, then that is ILLEGAL.
Now, if someone did this to you, would you consider it illegal?
How about this...instead of SHOUTING and posting pictures that only show there was a fight you post any reliable link that proves that your supposition that Martin sucker punched Zimmerman. You seem to know what happened so it should be easy.