I successfully kept rabbits and chickens together. I had 4 rabbits and 6 chickens living together in the same coop. The shared one big run. The rabbits had a safe place on the bottom of the coop with a hole just big enough for them, but to small for chickens. On top of the rabbit house, the chickens could fly up to roost and how nesting boxes to lay their eggs. Each section had a door on the back to clean out the poop. I wish I had a picture of the setup since it's probably confusing the way I am describing it.
The biggest issue was feeding. I'm sure you are well aware that corn is not good for rabbits and that is a big ingredient in chicken food. We had to have the chicken food in a place the rabbits couldn't touch it and the rabbit food somewhere else.
The rabbits lived to be a good 5-6 years until they ran away when we were moving or died of illness. It's quite the hassle having the two together but they managed. Now we have enough room for the rabbits to have their own hutch and the chickens their own coop.