No — there is currently no reliable public source that confirms Zach Thornton is left-handed.

Zach Thornton is a former American professional soccer player who played as a goalkeeper. He had a notable career in Major League Soccer (MLS) and represented the United States national team.

Thornton spent a significant portion of his MLS career with the Chicago Fire, where he became a fan favorite and was instrumental in the team's success, including winning the MLS Cup in 1998.

Known for his athleticism, commanding presence in the box, and shot-stopping abilities, he was widely considered one of the top goalkeepers in MLS during his playing days.

He also had stints with other MLS clubs and briefly played in Europe. After retiring from professional play, Thornton transitioned into coaching, contributing his expertise to developing new talent.