He made his MLB debut in the club's third game of the regular season, working one inning of a 7–1 defeat at the hands of the San Francisco Giants at Colt Stadium.

[2] For his rookie campaign, Zachary worked in 22 games, with seven starts, and notched a 2–2 won–lost record and 4.89 earned run average in 57 innings pitched.

As a Cardinal in 1971, he threw his only MLB complete game and shutout on May 27 at Busch Memorial Stadium, allowing only two hits to the Chicago Cubs and striking out three, with no walks.

Called up by the Tigers from Triple-A Toledo in May, Zachary became a reliable member of manager Billy Martin's bullpen, compiling a sparkling 1.41 ERA with one win and one save in 381⁄3 innings pitched as Detroit captured the AL East title.

[4] Zachary's final MLB line included a 10–29 won–lost mark (for a poor winning percentage of .256), with an earned run average of 4.57 and two career saves.