That year, he was accompanied by two other hoods as they participated in the "hit" on Kalo and Mirt following the arrival of the USS Enterprise landing party, killing Mirt. A short time later, he captured Captain James T. Kirk as he escaped from a warehouse where he was being held by three of Bela Okmyx's hoods, and returned him to Krako's headquarters.
After Kirk refused to help Krako, and was put on ice in the headquarters cellar, Zabo and a second hood rushed into the room where Kirk was held and had feigned an injury, calling for help. He tripped over a trip wire Kirk had placed in front of the room's entrance and was subsequently incapacitated by Kirk after he threw a blanket over his head and gut-punched him.
Following Kirk's escape and later return to Krako's headquarters, where Kirk and Spock had captured Krako, Zabo would be rendered unconscious by a punch to his glass jaw. After recovering from his second knockout of the day, he would round up a number of Krako's men and lead another "hit" on Okmyx's gang in retaliation, only to be stopped by the USS Enterprise's phasers set on "stun" around a whole city block. (TOS: "A Piece of the Action")