At the windward mark (without offset) A enters the zone clear ahead of B. Both starboard tack. By rounding the mark A opens a gap to the mark and b sails inside between the mark and A. A sails a gybe set and B take a crash gybe to avoid contact and protests.
Version 2: A sails one hull length downwind starboard and gybes then inside the zone.
Version 3: B is at the beginning on port and tacks in the zone. Is there a difference?
Version 4: While gybing, B has contact with A.