How come when i play Call of Duty WaW zombies, I lag?

check your router settings if you have one or it might just be your isp throttling you, like mine does.

Sounds as if you need a new ISP. If you play during what they consider peak times they are probably throttling your speed.

Try checking here for your router and make sure you unlock the ports for WaW. It usually has the same issues that all CoD games have in that regard. You can find the port listings at the same site I linked using their game-specific configs.

Barring that make sure when you’re playing there are no latency-sapping programs running in the background like torrent programs, Steam downloading updates, antivirus scans and the like. Also adjusting graphics options down a notch or two can help with your latency on many games.