Complex sentence: He joined MLS as an assistant for Lothar Osiander with Los Angeles Galaxy reaching the MLS Cup final the first year of the league, and assumed head coaching duties when Osiander was fired early in the 1997 season.
Split into simpler sentences: He joined MLS as an assistant for Lothar Osiander with Los Angeles Galaxy reaching the MLS Cup final the first year of the league. Zambrano assumed head coaching duties when Osiander was fired early in the 1997 season.