After time out of the spotlight, Zac resurfaced at the Toronto Film Festival and is now said to be healthy and happy as he focuses on his movie career.
A source told E! News: "He's healthy, happy and not drinking. He's taking time to focus on work."
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An insider also told People, "He's doing great. He's taking care of himself and it shows."
The news of his rehab stint will no doubt shock fans of Zac, who has managed to stay away from the Hollywood party scene.
He will next appear on the big screen in Parkland, which focuses on the days surrounding the assassination of JFK in Dallas in 1963.
Zac plays Jim Carrico, the real-life doctor who battled to save the president at Parkland Memorial Hospital after he was shot.
"It's a very surreal experience for me," he told USA Today of working on the film. "It feels very mature and really interesting. It's a whole different kind of filmmaking and I feel blessed to have been a part of it."