Zac Efron and Russell Crowe are in talks to star in 'The Greatest Beer Run Ever'.

The new flick is director Peter Farrelly's follow-up to the Oscar-winning 'Green Book' and is based on the book 'The Greatest Beer Run Ever: A True Story of Friendship Stronger Than War'.

Apple Studios are in discussions to finance the project with Bill Murray being courted for a supporting role.

The book, by Joanna Molloy and John 'Chickie' Donohue, is based on a true story of how John decided to track down and have a drink with his childhood friends in the Army - while they were serving in the Vietnam War.

Peter has written the script with Brian Currie and Pete Jones and the film will be produced by Andrew Muscato, David Ellison, Dana Goldberg and Don Granger.

Zac is set to play the role of Donohue in the flick, with the expectation that shooting will begin in August – likely in Australia or New Zealand.

Viggo Mortensen, who worked with Farrelly on 'Green Book', had previously been in talks to join the project in a supporting role – although it is unclear if he is still involved.

Russell recently starred in the action thriller 'Unhinged' as a man who becomes hell-bent on revenge when a woman honks her horn at him while driving and he felt the film was an accurate portrayal of the anger that can be seen across the world.

The 56-year-old actor said: "I started to realise this type of rage is happening continuously all over the place, that seems to be a place we've arrived at in Western society.

"For our example it's a guy using a car, but it's also people stepping into places of worship, schools, nightclubs, and opening fire. It's people going crazy in a supermarket over toilet rolls."