Conversion of zip files to 7z file format
You can easily re-pack various compressed archives from one format to another, by extracting the original file (in this case ZIP) and compressing it again to a 7Z format, which is what zip to 7z conversion pretty much represents. The difference is usually in the compression ratio and thus resulting file size.
Open ZIP file
Open 7Z file
Related software
Popular open source file archiver with a high compression ratio
A compression utility for OS X
A full-featured compressed archives manager
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Mac version of the popular utility
A Linux application used as frontend for popular compression tools