Ow... my stomach...
Zone's and Watts's fathers were publicly executed by the Galbadian government to set an example for other would-be rebels during the Timber War. In vengeance, Zone and Watts took over the Forest Owls in their fathers' stead.
Despite being the group's leader, Zone often lets Rinoa do the talking and take responsibility for the tougher tasks. He gets coincidental "stomach pains" whenever much pressure is laid upon him or he is asked to participate in the more dangerous missions. One notable example is when he decides to let Quistis have his train ticket to escape Timber, but when she tries to thank him he doubles over in pain and runs away.
Later on Zone and Watts end up on the White SeeD Ship, his stomach pains now absent. When Squall tells Zone of Rinoa's comatose state Zone becomes angry, cursing Squall for not protecting her. He heads to the helm, and if Squall follows him there Zone has calmed down and explains he has learned how to pilot the ship.