The center should be occupied with the blitzing linebacker in the A gap and seeing the looping edge blitzer can be difficult. One key to this pressure's success is a great take off from the DL to force the QB to step up into the pocket and to give the edge blitzer a better angle to the QB. The edge blitzer should start as if off the edge then loop inside off of the penetrating DL and ILB.
Film of the Cleveland Browns running a loop edge blitz can be seen here. The Browns blitz is not identical to the diagram but is a good example of the looping edge blitzer technique.