Zombo played in 64 games with the St. Louis Blues in the 1991–92 season, earning 18 points, helping the team make the playoffs. In the first round, the Blues were eliminated by the Chicago Blackhawks, and Zombo had two assists in six games. His offensive numbers continued to slump during the 1992–93 season, as Zombo had no goals and 15 assists in 71 games with the Blues. Zombo added a point in 11 playoff games, as well as a poor rating of −9 as the St. Louis lost in the second round. Zombo continued to struggle in the 1993–94 season, earning 10 points in 74 games with a −15 rating during the regular season. Zombo was suspended for 10 regular season games after NHL Vice President Brian Burke ruled that he deliberately hit linesman Kevin Collins in a game against Dallas on January 9, 1994. In the playoffs, the Blues were swept by the Dallas Stars in the first round, as Zombo had no points in four games. In the lockout shortened season in 1994–95, Zombo appeared in only 23 games, earning five points with the Blues, before going pointless in three playoff games. On October 2, 1995, the Blues traded Zombo to the Boston Bruins in exchange for Fred Knipscheer.