A native of Windsor, Ontario, Zack was selected 13th overall by the Buffalo Sabres in the 2009 NHL entry draft. He began his NHL career with the Sabres in the 2011-12 season and was traded to the Canucks in February 2012. In December of 2015 Zack was traded from the Montreal Canadians to the Edmonton Oilers. Zack scored his first goal as an Oiler on January 18th, 2016, and he has established himself as a fan favourite in Edmonton after an impressive regular season and playoff performance in the 2016-17 season. In the summer of 2017, Zack signed a three-year contract extension with the Oilers.

Internationally, Kassian played for Canada at the 2009 IIHF World U18 Championships and with Canada’s U20 team at the 2011 World Junior Championships.