iOS 7: Unzipping zip files, natively
As far as I know, you need to use third-party tools like SSZipArchive or ZipArchive in order to work with zip files.

Using SSZipArchive, the line below would unzip a zip file:

[SSZipArchive unzipFileAtPath:path toDestination:destination];


Edit:

It turns out that in iOS 7, Apple added support to natively unzip files in iMessage and in the Mail app! Not sure if this is 100% related, but it might help. See this link for more info.