I think so
My only use of Azek was for a 7 wide door sill and is very strong. Any material ..other than popcorn... is very strong when loaded in compression. AS when placed at the bottom and loaded on top with weight. It's usually the joinery that fails, so you may want to reinforce the corners with Azek blocks to screw the side panels into. The overall weight of the entire thing would probably be around 100 lbs or so, not a whole lot. I don't see any structural issues in that design.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)