When you’re using both chicken and shrimp in a recipe, cooking the chicken first is the way to go, as the chicken takes longer to cook. Once you remove the chicken, the shrimp will cook very quickly in the hot skillet. I don’t recommend cooking them both in the skillet at the same time unless you have a very large skillet. Otherwise, even if you wait to add the shrimp until the chicken are mostly done, you won’t get the browning you want on the chicken if you overcrowd the pan.