coach_billyg here... OP, take a look at my team under this account. they are not a great team by any stretch of the imagination. but look at their team this year and some of the top 25 d1 teams in your world.
the point being, the jump-out-and-bite-you strength of the zone defense seems to be, you can do more with less. this team has 5 freshman and is noticeably outmatched talent wise by probably just about every top 40 team. i don't think i would have come close to 17 rpi with the press, which is by far my most familiar and best defense, so usually i would expect to do way better with it than zone, considering i have made it past the 1st round once with the zone and have won 16 titles with the press. this team's upperclassmen were recruited on D range prestige, so with 5 freshman, they have absolutely no business being a top 20 rpi team. i think i would really, really, really struggle to win a NT even with a much more talented zone team, i just don't think that is zone's forte. but because i get almost 30 minutes a game out of all my core players, i hardly have to play those 5 freshman at all. its a huge advantage! more with less... and less with more :)