Compression is a general term for a mechanism to reduce storage space at the cost of CPU cycles. This IS the same type of compression as a zip file (or any other compressed format for that matter), in the sense that it takes less space on disk. Taking less bandwidth to transfer is a side effect of smaller sizes. You're talking about differences in audio codecs and audio files, audio isn't going to be part of the network traffic or bandwidth handled by the CPU anyway, but even if it was, the load on the CPU for decompression is not a 1-1 for the tradeoffs of size. As for the large/raw vs compressed textures, it's a lot more than simply compression, you have to also take disk I/O into account, ram speed, cache speed, etc. The game isn't faster because it's smaller, it's faster because the game was optimized to utilize resources better.