like both destroying a special ship
You're right, but could potentially be incorrect here. Only the Empire gets bonus cards for destroying a special ship - they get 2 Bonus Orders for defeating the Millenium Falcon.
The Rebels DO NOT get Bonus Orders for destroying the Executor. Rather, their bonus is that they've cut off the Imperial supply of TIE Fighters (since you can only use one TIE one time each - neither side has infinite troops as in normal RISK titles).
Make sure to play with the clarified rules if you aren't already. Balances it a LOT. https://boardgamegeek.com/thread/1447610/some-rules-clarific...