Although she plays a live-action character in Maleficent, she should be fairly used to the process Disney uses to bring these sorts of characters to life on the big screen.
Plus, she’s previously done voice work for other movies, including the Kung Fu Panda and Shark Tale.
Jolie should have pretty good experience working on this sort of project.
The One and Only Ivan is also supposed to be similar to a lot of the Disney live-action remakes the company has been putting out over the past few years, with a mix of live action and CGI animals.