The outside zone is probably the most famous running play in the NFL, perhaps behind Power O. Terrell Davis and the Denver Broncos dominated the NFL for years running that play, and it's become a fixture for a lot of teams. Offensive line coach Alex Gibbs was one of the key people to develop the concept, and he's implemented it with several NFL teams. If you want to know how the play works, listen to the master explain it (hat tip: Football Outsiders -- a column you should really read, too).
The Buccaneers are great at stopping the outside zone, though, because of a couple of different reasons. One big one is Gerald McCoy, who will kill any outside zone play run to his side. He just gets into the backfield too quickly, and guards can't reach block him. Michael Bennett was great at that, too, but sadly he's with the Seahawks. Lavonte David is another reason, as he can creep into the backfield between blockers and chase down plays from the backside. The Bucs' tendency to blitz defensive backs and stunt their defensive line helps as well. Safeties who are comfortable in the box and can shed blockers and make the tackle are yet another factor.
But Alex Gibbs gives us a hint in the video (6:40):
"We don't block corners, we block safeties. We make corners tackle. They're as shitty as tacklers in our league as they are in yours."
This is easy to see on film, and not just with outside zone plays. Many teams will have their wide receivers run at an angle toward the safety on running plays, completely ignoring the cornerbacks.
That's the key for the Buccaneers: they don't want cornerbacks who can't tackle. They don't want anyone who can't tackle. That was probably a factor in letting E.J. Biggers walk in free agency, but it's also been obvious in the players they've added to the team this year -- and the ones they didn't. Note that they didn't come close to anyone who struggled as a tackler.
Second-rounder Johnthan Banks is a physical cornerback who will hit people in the running game. Darrelle Revis is very aggressive in run defense and will bring the ball carrier down: he's no Deion Sanders. Even the undrafted free agents fit this: aside from Branden Smith they're tall, well-built players who at least have the physical aspects to be quality tacklers.
Fundamentals are important for the Bucs, and they do everything they can to reinforce those throughout the offseason. The Bucs will not take players who won't tackle, which is why are very comfortable letting their cornerbacks tackle people in the run game. And that's certainly a big part of why they had the league's best run defense last season.