Q) how are the ONE zones defined
A) http://www.tarom.net/ba/explorer.pdf if you look here you will see a map, that will give you a brief outline of what each zone is defined by.

Q) how many flights am i allowed on a ONE ticket
A) up to a max of 20
you are permitted 4 Segments (segment is a flight with 1 continuous flight number) per continent/Zone - you are allowed 6 in the US - you are only allowed 2 stops in the continent/zone of origin (but you may still use the 4/6 segments)
trans pac/ atl flights do not count towrds your zone allowance

Q) can i end my itininary in a differnet city than i purchased it in,
A) yes you can for example start in CAI and end in DXB
4. ORIGIN-DESTINATION SURFACE PERMITTED:
112N . -WITHIN COUNTRY OF ORIGIN.-BETWEEN U.S.A-CANADA
113N . -WITHIN AFRICA
114N . -WITHIN THE MIDDLE EAST
115N . -BETWEEN HKG-CHINA
116N . -BETWEEN BANGLADESH-BKK/SIN
117N . -WITHIN SOUTH AMERICA
118N . -BETWEEN MAYLAYSIA-SIN