Well, Shannahan has historically had one of the very best Zone Blocking Schemes in Football. The problem is that it is hard to determine what you call moving the Defense "sideways by holding" and "Sliding" which is what you call the technique employed by a zone blocking scheme.
In that scheme, you look for OLs who have very good feet, very good mobility and have the ability to implement Reach Block techniques. This is known as sliding. The idea is to create space by creating movement in the front seven and disrupt gap responsibility. This is why cutback runners do so well in this kind of scheme. This scheme is also famous for cut blocks. I don't love this scheme and I think it's dangerous but it's legal and very effective.