After going pointless in ten games to start the 2018–19 season, Zacha was assigned to the Binghamton Devils of the American Hockey League (AHL) on 2 November 2018.

[5] On 13 July 2022, Zacha as a restricted free agent was traded by the Devils to the Boston Bruins in exchange for Erik Haula.

[13] Zacha found success in his first season in Boston, mainly playing as a wing on the first line alongside Patrice Bergeron and Brad Marchand.

He would also register six assists in the 2023 Stanley Cup playoffs, playing in all seven games of the Bruins first round loss against the Florida Panthers.

[16] After a four game stretch where he scored five goals and two assists, Zacha was named the NHL Second Star of the Week in mid-March.

Zacha would score the lone goal in a 1-0 quarterfinal victory over the United States, and would eventually help the Czechs to a gold medal.