Macs handle zip files out of the box

Mac can both unzip Zip files and create them, without any additional software!! It appears that this feature was made available with the release of Tiger.

To open a zip file, simply double clip on it and you'll see a new folder appear in the finder within a few seconds with the name of the zip file. Dead simple. No extractors or unzippers needed, unless you're dealing with .RAR files.

To create a zip file, simply select a file, folder, or group of files and right click on them. In Tiger choose Create Archive of . . . In Leopard choose Compress "your-filename" from the context menu. In a few seconds you'll have the zip file, which you can rename if neccessary.

See: Apple Pro Tip of the Week - Making ZIP Files (Compressed Files) in One Click