Born in Valencia, Carabobo, Zuloaga was a left-handed curveball specialist. He started to be known as El Mono when he entered the Venezuelan Professional Baseball League in its inaugural season of 1946. It was a moniker that he proudly used throughout his life.

Previously, Zuloaga pitched for the Cervecería Caracas of the First Division from 1942 through 1945, then moved with the team when it relocated to the new circuit in 1946. He spent his entire career with the franchise, including when it was called the Leones del Caracas, pitching in the league until the 1955–1956 season.

In addition, Zuloaga represented the Venezuela national team in the Baseball World Cup in 1944 and 1945, leading his team to win Gold medal at both championships. In 1944 he led all pitchers with a 3–0 record and a 0.94 earned run average, and went 4–0 in 1945 to set a tournament all-time record for the most wins, also setting an all-time mark for most consecutive win decisions with his 7–0 undefeated streak at the event.

Zuloaga started slowly with Cervecería in his two first seasons, going 0-2 with a 4.37 ERA (1946) and 5-2, 1.91 (1946–1947). His most productive season came in 1947–1948, when he posted a 10-4 record and a 2.51 ERA in 118 innings of work, leading the league in starts (16) while tying with Vargas' Don Newcombe for the most wins and shutouts (3), and ending third in ERA. On the day after Christmas, Zuloaga hurled the first important single game in Venezuelan league history, a one-hit 5–0 masterpiece for Cervecería against Max Surkont and the Patriotas de Venezuela club, during which he permitted a leadoff single, struck out 10, walked two, and did not allowed a runner to reach second base.

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