Prior to turning professional, Zalewski attended the Rensselaer Polytechnic Institute where he played two seasons (2012-2014) of National Collegiate Athletic Association Division I hockey with the RPI Engineers, registering 21 goals, 26 assists, 47 points, and 75 penalty minutes in 71 games.
He is currently playing with the Vancouver Canucks of the National Hockey League (National Hockey League). On March 14, 2014, the Vancouver Canucks of the National Hockey League signed Zalewski as a free agent to an entry-level contract. On April 12, 2014, Zalewski made his National Hockey League debut skating 11:47 with the Vancouver Canucks in a 5-2 loss to the Edmonton Oilers.
On July 8, 2015, with Zalewski unable to retain an National Hockey League contract with the Canucks, he opted to remain within the organization by signing a one-year AHL contract with affiliate, the Utica Comets.
On January 20, 2016, Zalewski signed a two-way, one year National Hockey League contract with the Vancouver Canucks and subsequently was recalled the same day.
