dmg The .dmg extension file is a disk image file, formatted by Apple Macintosh OS X. These files are usually used to install programs on computers having Mac OS. These files cannot be opened easily on Windows Operating Systems as they are intended for use on Macintosh Operating Systems.
zip The .ZIP file extension format is a file archive and data compression format originally developed and released in 1989 by Phil Katz. With compatible zip format software, a file or a group of files can be packed (compressed) into a single .zip archive which can later be unpacked (decompressed). The zip file archive format facilitates the distribution of multiple files as single archives particularly over the internet and networked systems. Many operating systems have native support for the file format and can usually open zip archives without the need for third party software. Microsoft windows for instance has had native support for the ZIP format since Microsoft Windows 98, similarly Apple's Mac OS includes ZIP support through its default archive file handle Archive Utility.