Disney's Magical Express does have zones, but resort drop-offs aren't necessarily decided by these. The purpose of the zones, for passengers runs, is that the maximum number of resorts per bus is 4 if the bus stays in one zone, or 3 if the bus has guests for resorts in more than one zone.
Beach Club is in the EC zone, which also includes Yacht Club, BoardWalk Inn, BoardWalk Villas, Caribbean Beach Resort.
The MK zone has Grand Floridian, Contemporary, Bay Lake Tower, Polynesian and Wilderness Lodge.
The DD zone has Saratoga Springs Resort, Old Key West, Port Orleans French Quarter, Port Orleans Riverside, and Fort Wilderness Resort & Campground.
The AK zone has Animal Kingdom Lodge, Animal Kingdom Villas, Coronado Springs Resort, Pop Century Resort and all three All Star resorts.