The executor was destroyed by crashing into the Death Star. The A-Wing hit the bridge after the shields were lowered by a combined bombardment from the rebel fleet, then fighters took out the shield generators. Do some research.
The executor's shields stood up to 3 star destroyers colliding with it at relativistic speed as they dropped out of hyperspace in one incident.
You don't like the EU?
Tough ****. It's canon, get over it.