Who be Zerah?

According to 2 Chron 4, in the 11th year of Asa (902 BC), Zerah the Cushite tried to invade Judah by way of Mareshah (just south of Beit Guvrin). Since the reign of Asa (912-871 BC) corresponds well with the reign of Osorkon I (924-889 BC) of Egypt, a Libyan, not a Cushite, Zerah must not be the name of a king, but of a military commander. Unfortunately, even with all Zerah’s chariotry, he was struck down as far as Gerar (Tel Haror, 31°22’54″N, 34°36’26″E), due to the military preparedness and superior position (higher usually beats lower) of Asa’s troops. Asa also managed to get a significant amount of booty from the villages surrounding the then-small town of Gerar and from Zerah’s own troops. However, Chronicles does not state Asa acquired the newly devastated territory.