Between the TIE fighters; far superior technology, manoeuvrability etc, their ability to fly far above any WWII era plane, and the shields on Lambda shuttles, I really don't see the SD losing a single ship. They pick off any attacks with impunity and the shuttles just zoom about the globe devastating cities, bases, shipyards etc. It's over in a week. And that's before any AT-ATs do anything, before any stormtroopers take the field, any of that. The air superiority is too great, as is the defensive technology.