Mine are in the backyard - not together. From what I have read it’s good to keep them 20 ft apart or more. There is at least one killer that I recall I think it’s a respiratory illness chickens can pass to quail and it’s pretty deadly for them.
It’s in the air (I’ve read) there isn’t much you can do about it except keep them separate if you have both it limits exposure - so far I’ve not had any sickness from the chickens. I have 3 - and they can be pretty gross - those big chicken patty poops omg lol mine are some feet away from each other. The chickens come out but they don’t mess about with the quails. My sister also has a few chickens and a few quail same situation and hers are good as well.
Now I’ve had mystery deaths but not from sickness except 1 but it wasn’t from the chickens in fact I’ve no idea what it was as no amount of research has helped except perhaps bad kidneys. It happens. Best of luck I love quail and chickens but there is just something about a quails face I just want to pinch their little feathered cheeks *sigh*