the WR runs the more the DB has no idea what the WR is going to do so they have to respect every option. The DB here actually plays great defense before the pass because he has to stay in front of the WR or risk getting burned for the TD, he stays inside so he can protect the greater portion of the field and makes a play on the ball in most throws.

That said Defense is always at a disadvantage because you can't cover everything. Defense has to count on mistakes or a poorly run route that gives the DB insight into what was planned. They also watch tape on the WRs looking for their cues or tells on how they move before going inside, outside or deep. This route is immaculate, going from full sprint downfield to a smooth plant and break. The ball is where the DB will have no chance at it if he is staying in front of the WR. Zach is money and so it the WR so the defender would never have made a play there unless he is clairvoyant.