A left-handed pitcher, he spent most of his early career playing for the Washington Senators, with whom he won the 1924 World Series.

Zachary's most notable collegiate game was on April 16, 1918, when he was matched against North Carolina State College's ace and future major leaguer George Murray.

[1] In the summer of 1918, Zachary joined the American Red Cross, and was assigned to duty in Europe during World War I.

While preparing to ship out, he tried out for the Philadelphia Athletics under Connie Mack, pitching in and winning two games under the name Zachary Walton, a pseudonym he used to preserve his amateur status.

He helped pitch the Senators to the World Series, where they faced John McGraw's New York Giants.

As the Senators' number-two starter (behind Walter Johnson), Zachary started Games 2 and 6 of the Series, winning both.

[2] Pitching for the Yankees, Zachary won Game 3 of the 1928 World Series, defeating the St. Louis Cardinals.

[1] Zachary was claimed off waivers by the Boston Braves in May 1930, and spent three full seasons with the team before he was signed by the Brooklyn Dodgers in 1934.

[2] He would often change paces and "slop" the ball at low speeds towards opposing batters to tempt them into swinging away.