I guess that exploding a book would work even if there is DRM but, at least with ePubs, DRM works by encrypting the book contents, so if you view any of the exploded files they are all 'gibberish'.
I would have thought that AZW3s with DRM would work the same way — otherwise what's the point of the DRM if the book can be copied simply by exploding it? Maybe Amazon supply samples without DRM.
Can you post a sample AZW3, (without breaking any copyright), that shows this behaviour? I can then have a play with it.