The moves announced Thursday are the first major ones under Andrew Friedman, who arrived in Los Angeles from Tampa Bay last month as the new president of baseball operations.
Zaidi, who was born in Sudbury, Ont., but grew up predominantly in the Philippines, joins the Dodgers as the 11th general manager in club history. He spent the last 10 years with Oakland, most recently serving as the club's assistant GM and director of baseball operations. Zaidi will focus on the major league club and player acquisitions.
Byrnes will supervise the Dodgers' scouting and player development operations after previously working for two of the club's NL West rivals, Arizona and San Diego.