He pitched in Major League Baseball for the Cincinnati Reds, New York Mets, Los Angeles Dodgers, and Philadelphia Phillies from 1976 to 1985.

While a member of the Tampa Tarpons in 1971, Zachry received notice of his military draft eligibility, but he failed the U.S. Army's physical examination due a severe childhood injury to his leg.

[3] He made his major league debut on April 11, 1976 as a relief pitcher; the Reds moved him into the starting rotation shortly afterward.

[4] For the season, Zachry compiled a 14–7 record, 2.74 ERA, and a team leading 143 strikeouts in 204 innings pitched.

After the season, Zachry had a hernia operation, and was in the process of recovering when he and San Diego Padres closer Butch Metzger were named co-winners of the National League Rookie of the Year Award.

[9] The hernia, coupled with a sore elbow, delayed Zachry's 1977 Spring training, and denied him the opening day start.

Following an 8–0 loss to Tom Seaver and the New York Mets at Shea Stadium on June 7, Zachry had a 3–7 record with a 5.04 ERA.

[12][13] Tom Seaver, meanwhile, engaged in a contract dispute with Mets chairman M. Donald Grant, and had requested a trade.

[15][16] Over the rest of the season, Zachry went 7–6 with a 3.76 ERA, and was the only Mets starting pitcher to post a winning record besides Seaver (7–3).

[21] On July 24, the Cincinnati Reds came to Shea Stadium with Pete Rose entering the game with a 36-game hitting streak.

[28] He won each of his first three starts, but then fell into a five-game losing streak in which his ERA was 6.93, and opposing batters hit .330.

[34] In his two seasons with the Dodgers, Zachry pitched exclusively in relief, except for one emergency start made in the second game of a doubleheader against the Mets at Shea on August 30, 1983 (he held his former team scoreless for six innings before giving way to the bullpen).

He appeared in games three and four of the 1983 National League Championship Series, both won by the Philadelphia Phillies by final scores of 7–2.

[40] According to the Mets, Zachry died at his son Josh's home in Austin, Texas, following a lengthy illness.