FileInfo.com - The File Extensions Resource

.PIZ File Extension

File Type	Zipped File
File Format	File
Common?	No
File Description	Typically a compressed .ZIP archive with the extension reversed; may be changed to hide the file type or to prevent opening; rename extension from ".piz" to ".zip" to open correctly.
Program(s) that open piz files	Mac: Smith Micro StuffIt Deluxe for Mac Windows: Corel WinZip; Smith Micro StuffIt Deluxe for Windows

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/piz