Wirelessly posted (iPhone 4s: Mozilla/5.0 (iPhone; CPU iPhone OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B179 Safari/7534.48.3)
There's a compression tool built into Mac OS X. Just select files, right-click and select "Compress x items". Or double-click a zip file to open. There are also 3rd party apps, such as StuffIt Expander or UnRarX or The Unarchiver or iZip
Do you want to extract them or create them?
Because both tools are already built into Mac OS X.
Double click on a .zip file to extract it, and select several files or folder and right-click and select Compress to make a .zip file.