Do not. It is not just a line connecting them. They're are float valves in those systems.
Your first diagram on this page looks correct.
I thought so NoL.
I mean, I thought about this real hard and figured that the compressors ran fine even without oil seperators and reservoirs or whatever before!
So I said to myself.
I know in parallel a seperator is needed to isolate the oil flow out of and back into each other but there shouldn't be a problem with some oil return in the suction return as like I said there wasn't any fancy things there before.