High School Career: Stephen Zimmerman Jr. attended Bishop Gorman High School in Las Vegas, Nevada, where he led the Gaels to four consecutive state championships, becoming the only player in Nevada history to achieve this at the large-school level. He amassed 114 career wins, making him the winningest player in the school's history. In his senior year (2014–2015), Zimmerman averaged 14.7 points, 10.1 rebounds, 4.2 assists, 2.4 blocks, and 1.2 steals per game. His outstanding performance earned him selections to the McDonald's All-American Game and the Jordan Brand Classic.​

College Career: Zimmerman played one season (2015–2016) for the UNLV Runnin' Rebels. During his freshman year, he appeared in 26 games, starting 24, and averaged 10.5 points, 8.7 rebounds, and 2.0 blocks per game. He ranked second in the Mountain West Conference in blocked shots and third in rebounding. Zimmerman declared for the NBA draft after his freshman season.​

Professional Career: Selected 41st overall by the Orlando Magic in the 2016 NBA Draft, Zimmerman played 19