I don't know - look at movies like Saving Private Ryan. Or Schindler's list. A lot of these have elements of oral history incorporated into the movie - the interviews at the start and end of the film.
If these sort of interviews were being used to set the scene and tone of the film, and then selecting half a dozen good sequences to explore in greater depth, it could be good.
on the other hand, what makes WWZ a good book it that it's almost a series of short stories set in the same world - and the fact that there are so many of them really establishes a good sense of what has happened. This might be harder to pull off with the limited time that a 90-120min movie allows