Can .zip folders created using Windows XP Pro be opened and extracted on Mac without any additional software? I am a Windows user, and I would like to send a compressed archive/folder to my colleague who is a Mac user. I do not want him to have to download any additional software to open and extract it. 

Can .zip files created using Windows XP Pro be opened and extracted on Mac without any additional software?  Is the file specification the same in Mac as it is in Windows?
Yes.

The PKZIP format used by Windows is understood by OS X and has been this way since about 10.3. The tool used to extract the contents is called Archive Utility and it is installed by default with every OS X installation.

Your Mac-using friend can either double-click on the archive in Finder to extract it or he can right-click/control-click and select the 'Open' option from the list of actions.