L5 seasons he wins about 90% leading at the half and only about 20 percent of the time when tied/trailing at half. L5 seasons league average is about a 78% occurrence of winning straight up when you lead at halftime, 75% of which you also cover. League average during that time is about 26% straight up when trailing/tied at halftime and 28% covering the full game spread.
Mike Zimmer is good with a halftime lead too: 85% full game win percentage and 95% against the spread when Vikes lead after two quarters. He and Bill O'Brien both became head coaches in the same season - back in 2014 in what must have been a vintage year for head coaching changes.