Whenever I've tried following the Zone, or even fat-modified Zone it always ends with late-night nut butter binges. I've found better results both performance and body-composition wise by simply going Paleo with minimal fruit and keep track of calories and grams of protein to make sure I'm getting enough of each. In the end I'm usually getting 60g of carbs a day at most, probably like 5-13% of my diet from carbs.
On the Zone, I'm supposed to be eating 1300, 1400 calories at 180lbs . . . Not enough to support my sanity. Right now, I'm eating about 2000 and still losing at least 2lbs/week. I would try tracking your Zone calories to see how much you're actually eating and see if you might be better off eating more food, period.