His best season at Hibs was 1964-65 during the 12 months they were managed by Jock Stein (Stein had a 62% win rate at Hibs). Hibs challenged for league and cup until Stein left before the end of the season to manage Celtic in March 1965. Cormack scored twice when Hibs won 4–2 against Rangers at Ibrox Park on 10 October 1964 in one of three victories against Rangers. The 4–2 win at Ibrox was three days after Cormack and Hibs had beaten Real Madrid 2–0 in a challenge match at Easter Road. Cormack scored the opener against Real volleying home a cross by Neil Martin. Stein was replaced by Bob Shankly with whom Hibs finished fourth in the league and lost in the Scottish Cup semi final to Dunfermline Athletic. Cormack played regularly with Hibs in Europe but was unable to progress past the quarter final stage. The most significant of Cormack's wins in Europe with Hibs was the November 1967 6-4 aggregate success against S.S.C. Napoli featuring Dino Zoff. Napoli won the first leg 4–1 in Italy. Cormack scored the third as Hibs won the second leg 5–0. Napoli were league leaders in Serie A at the time. Hibs had knocked out F.C. Porto in the previous round when Cormack scored a double in the 3–0 home leg win. They were eliminated 2–1 on aggregate in the quarter final by Don Revie's Leeds United.