Super-blocks (also called sub-systems) of your ASIC design typically implement highly specialized functions, such as video encoding and decoding, encryption, packet classification, etc...
ZeBu allows you to verify those super-blocks more exhaustively than any other approach, so you can build full confidence in your design as early as possible, even before full-chip integration.
This shows an example of a super-block performing H.264 decoding, mapped in ZeBu and interacting with an AHB bus transactor and a Display transactor.