From: http://www.differencebetween.net/technology/difference-between-zip-and-gzip/
Summary:
1. GZIP can achieve better compression compared to ZIP.
2. ZIP is capable of archiving and compressing multiple files, while GZIP is only capable of compression.
3. You can easily extract individual files from a large ZIP file, but not from a GZIP tarball.
4. ZIP is fairly popular on Windows, while GZIP is more popular on UNIX-like operating systems.
For more details please go to http://www.differencebetween.net/technology/difference-between-zip-and-gzip/.