Strict adherance to Sear's Zone specifications probably wouldn't be optimal, but, like all good things (including the HST program itself) it is open to individual tweaking to coincide with your specific goals.
If your sole goal is hypertrophy, then no, I don't think the Zone in it's raw form provides enough calories. BUT that doesn't mean you can't adjust your caloric intake.
Secondly, Sears shys away from ever spiking insulin which for bodybuilders is desirable after a workout. Again you could modify the diet for the insulin spike.
Duchaines and Lyle's isocaloric diet recommends an equal split of calories for fat, protein and carbs. But they don't stress balancing these ratios for each meal. I've tried the isocaloric diet, but I don't feel (for me anyway) it provides the same feeling of satiety, and overall wellness like the Zone does. Sears is a little more picky over his carb choices, and his aversion to grains and processed carbs is probably just what the doctor ordered in my case.
Adopting the Zone diet is the best thing I ever did for my health/weight. Of course, I'm not looking for insane mass. Weightlifting is just another piece of the puzzle in my overall health and fitness program.
Do I think the Zone does anything magical based on existing nutritional science? Nope, but it works like magic for me, and I'm sticking to it.

Of course, I feel I will be saying the same thing about HST within time.