It says that Avent's move was "part of a planned transition for the studio and team" and had been known internally for months.
To ensure a smooth progression, Zynga's VP of Games, Chris Plummer has stepped in to run the Boss Alien team in Brighton, UK, which is currently working part of the team working on the much anticipated CSR Racing 2, which is now due for release in the second half of 2016.
"Chris Plummer has been leading the team over the last few months as key driving force for the group," Zynga states.
"Chris is an experienced, well regarded leader at Zynga and NaturalMotion having been with the company for nearly 2 years."
He previously worked at DeNA's San Francisco studio, and before that was with EA for 13 years.