Does Delta even have a Zone 4?
In general I agree with the absurdity that "Zone 1" is usually the last to board the plane. By the time Zone 1 is done (at least in ATL during peak hours), the plane is probably 80-90% boarded. Sky usually guarantees a carry-on, but it is quite normal to force a portion of Zone 1 to check bags. "Priority boarding"... mmhmm, sure.
