Interestingly, this probably bodes well for Zimmerman in the long run, too. By paying the settlement the insurance company may have acknowledged that Zimmerman was acting as a volunteer "agent" of the HOA when he shot Martin. Under the bylaws of every HOA I've ever dealt with, any volunteers who work for the HOA as board members or in another capacity are indemnified against any lawsuits that are brought against them. Once Zimmerman was acquitted of the criminal charges, he may very well have the right to compel the HOA to pay any legal bills and financial settlements from civil lawsuits related to the incident.
If the HOA’s insurance policy is an “occurrence” form contract, or has an aggregate coverage limit that met the amount of the settlement, then there is nothing left under the policy to pay out. And the Martins and their bottom-feeding lawyers are SOL.