[1] During his active career, Zimmerman threw and batted right-handed, stood 6 feet 2 inches (1.88 m) tall and weighed 185 pounds (84 kg).

[4][5] Led by Mauch, and with Zimmerman catching, the Millers won the American Association and Junior World Series championships.

The Cincinnati Reds then signed him as free agent, and he spent the full 1960 campaign with their Triple-A affiliate, the Seattle Rainiers, where he batted .279 (a 100-point improvement over his previous year's average) with six home runs in 82 games.

He made the Cincinnati squad out of spring training as a backup and when the Reds traded away starting catcher Ed Bailey in late April, Zimmerman not only secured a roster spot, he became the club's most-used receiver during their National League pennant-winning season.

[10] In 1967, Zimmerman played in 104 games as Battey was troubled by health issues;[3] his 6921⁄3 innings caught were tops on the team that season.

[12] After Battey's release in the off-season, the Twins traded for catcher John Roseboro, and Zimmerman went back to being a reserve player during the 1968 season.

[4] Zimmerman and Don Leppert, his counterpart with the Blue Jays as a coach-umpire, are the last two active coaches to umpire a Major League game.