The Zone is a bunch of pseudoscience. If it is useful at all, it is in getting people to become aware of macronutrient ratios (thinking in Zone blocks). But, remember, before the Zone, athletes simply thought of their food in grams and accomplished the same thing.
The Zone prescribes a 40C-30P-30F ratio for fat loss via caloric restriction. It claims to provide optimal control over insulin levels for most people. This is a laughable claim. If the Zone works at all, it is probably because 40% of calories as carbohydrate is actually superior to the SAD (50-70% carbs). Also, the "preferred carb sources" list is far superior to most of the junk that people eat on SAD.
The Zone, as described above, doesn't serve most athletes well. Carbs are too high, fats too low, and the fat/caloric restriction just hammers you after a while. Robb Wolf advocates cutting some of the carb blocks and replacing them with fat blocks in a 1C:3F ratio, which can shift the macronutrient ratio more favorably toward moderate carb (10-25%) and fat (45-70%). (Keep in mind that the only reason he did this was because CFHQ was so bent on promoting the Zone in the first place -- or at least, that's my understanding. If Robb had had his way, he would have simply dropped the Zone nonsense altogether and focused on food quality, with macronutrient tinkering for more advanced athletes who need it.)
Then there's the "Athlete's Zone" that essentially doubles the fat blocks, or more. Some are at 3x-5x fat (and in some cases, even greater than that).
When you take into account these modifications, now you're sitting at something like 15C-25P-60F (%, not blocks), give or take. This is a far cry from 40-30-30.
If you want to weigh and measure your food and tinker with macronutrient ratios, go ahead and do that. If you want to use Zone blocks to do that, that's fine. Just don't buy into the idea that the Zone or even the Athlete's Zone is grounded in science. It is useful as a way to think about macronutrient ratios, and as a way for you to easily track and modify your intake. (Add 2 fat blocks every week and see how it affects you.) But you don't need the Zone to do this.
The Zone is a reasonable accounting system. There is no magic in the 40-30-30 number or even the 2x-5x fat blocks. Figure out what works for you.
And stay the hell away from any food product that has the Zone stamp on it. That stuff is pure garbage.