loaded the stl into simplify 3d, sliced with 0% infill.
perfect hollow shell.

so that aspect you can leave to the slicer.

And as the shell will print cleaner with the windows in, I'd do that and then use a rotary tool (dremel type thing) to cut the winodws out manually.

Sometimes you just get stl files that do not work with any editing software.

have you tried using the 'drainage hole tool' in the resin slicer to partially remove the windows and floor ?
If nothing else it makes it easier to file into the right shape.