zip is not a solid archive. Each file in a zip is compressed independently without referencing data from other files, so zip files can't exploit redundancy betw

zip is not a solid archive. Each file in a zip is compressed independently without referencing data from other files, so zip files can't exploit redundancy between files for better compression. tar.gz files compress the concatenation of all files, using redundancy between files to achieve better compression ratios. Note that gzip and zip use deflate which has a small 32KB window, so if the repetition is more than 32KB apart it cannot be used for compression.