Zac Efron is in talks to join the cast of 'The Greatest Showman on Earth'.

Zac Efron

Zac Efron

Variety reports that the 28-year-old actor has been approached by Fox to star alongside Hugh Jackman in the movie, which tells the true-life story of celebrated circus owner and entertainment impresario P.T. Barnum, who was responsible for a number of hoaxes.

The contemporary musical has been in development since 2009 with 'Sex and the City's Jenny Bicks set to write the script and Chernin Entertainment, Laurence Mark and Hugh producing.

Hugh will play Barnum - who created the three-ring Barnum & Bailey circus - in the film which is set for a December 2017 release.

The musical will be a return to his roots for Zac, who first found fame in Disney's 'High School Musical'.

Meanwhile, Zac's 'Baywatch' co-star Kelly Rohrbach recently praised his "insane" body after he bulked up for the movie.

She told E! News: "He obviously got in insane shape for the movie - insane! He was really disciplined and dedicated about it. We obviously had trainers help us and all that but by the time most of us got there, we were like, 'Eh, we'll work out next week.' He was on it."

And Zac, who dropped to just five per cent body fat in 12 weeks thanks to a strict low-carb diet and working out five or six days a week, often twice a day - is proud of his physique.

He said: "I'm probably the physically strongest I've ever felt.

"Not in terms of bench press or how much I can squat, but in how quickly I could get out of this room and destroy everything in my path."