I play zombie panic all the time and I see how you could say there similar but I think the huge difference in this would be the one hit tag instead of ZPS 4 hits.
On top of that there is a much greater variety of weapons within CSS that do much more damage and knock back, unlike ZPS where sometimes you can put an entire clip into a zombie to kill it and other times you could put 5 rounds into it to kill it.
Map variants in CSS are also a big difference because its much easier to put objectives into a CSS map than it is for a ZPS map. Most player made maps in ZPS are ZPS instead of ZPO or ZPA and the ZPO maps I have seen are usually just crude variants of Cabin which suck imo.
I rarely play zmod anymore cuz it seems its all retard who like LOTR. I kinda gave up on them and moved to GG
roy_highway?
I like escape maps too. some are just fun.