Can I wash Roxton zipped couch cushions?

I have a Roxton chesterfield with 3 cushions (you sit on them); Each cushion has a square of foam inside, covered by zippered cases, similar to a pillow case. I want to take the cases off and wash them in the "gentle" cycle of my washer, but I wonder how difficult it will be to insert the foam back into the case after....it appears to be a "snug" fit, but perhaps there's a way to do this.