Rarely did LSU bring more than 4 defenders against UK on the pass rush. They were able to get pressure to Pat Towles often with a zone blitz. The zone blitz is designed for two defenders to attack one offensive lineman (normally the offensive tackles). As the offensive lineman engages the inside defender, the defender will back out and become a zone pass drop defender. The outside defender now will have a better angle to to defeat the pass set block of the offensive tackle. It is something offensive lineman work nearly everyday in practice, but when the outside defender is in the top 10% of speed, it becomes a very difficult block.
A second result of the zone blitz is the dropping defender will be dropping to the area where a "hot" route will be sight adjusting. Often QBs and WR's are trained that if the outside backer crosses the inside WR face, he should go and replace that linebacker and the QB will throw "hot" to that spot. With the zone blitz, the linebacker is giving the QB and the WR a false read because a lineman will be replacing the linebacker's responsibility in zone pass coverage. Thus the name, "zone blitz":