While attending the
University of Akron, Zajac continued to play with his youth club
Sigma FC in the summer in
League1 Ontario, beginning in 2015. In 2016, he made 13 league appearances for Sigma, scoring five goals. The following year, Zajac made six appearances and added three goals. In 2018, he scored a career-high seven goals in eight appearances. He scored back-to-back hat-tricks on May 12, 2018 against
Windsor TFC and May 19, 2018 against
Ottawa South United. On January 8, 2019, Zajac signed his first professional contract with
Canadian Premier League side
Forge FC, joining former
Sigma FC coach
Bobby Smyrniotis. He made his professional debut as a substitute in the
inaugural CPL match against
York9. In March 2021, it was reported that Zajac signed with Watra Białka Tatrzańska of the
Polish fifth division. In June 2021, he trialled with Polish club
OKS Stomil Olsztyn. In July 2021, Zajac signed with
II liga side
Olimpia Elbląg. He left the club by mutual consent on November 30, 2021. In 2022, he played with
Guelph United F.C. in
League1 Ontario. ==International career==