Ducks are pretty tough and a whole out larger than a chicken.
We once put some baby ducks in with the chickens (30+ years ago before knowing better). A couple of chickens were bullying them and pulling most their feathers out. It only lasted a few weeks till the ducks got bigger than the chickens and it wasnt long before the Reckoning Day.
Those baby ducks (but bigger than the chickens) stood up for themselves and went on an Chicken Ass Kicking Spree.
I had to build another pen just for the ducks because they would have probably killed the chickens if i hadn't got them apart. The ducks would keep the chickens corralled up on one end of the run, and if any chicken went toward the feeder or water, the ducks would beat them down and send them back into the corner hiding. They remember the mistreating the chickens did and when free ranging if a chicken got near a duck it was ass kicking time.