During the 1960s, Zirkle attended Duke University. He began playing football for Duke Blue Devils in 1965, as part of the defensive line. Over the next four years, Zirkle became a major part of the Blue Devil's and their success during the 1960s. Playing Defensive tackle, he became the team captain in his senior year in 1968. At the end of his senior year, he was selected to play in the Blue-Gray Classic, becoming only one of six Duke player's to be selected for All-Star games in the 1960s. Zirkle was also the recipient of the Micah Harris Trinity Teammate Award, and the Blue Devil Club Award by Duke alumni to recognize Zirkle’s unique contributions.