# How to convert the existing zip files to 7z with 7-zip comand line

7-zipconversionpackerzip

I'd like to convert a couple thousand zip files to 7z, with maximum compression and multithreading enabled.

Also in another place. Like c:\temp\file.zip to f:\converted\file.7z

You can use arepack (included in atool command suite) to convert between archive formats. Combined with a little bash, it makes easy to convert a bunch of ZIP files to 7z:
for f in *.zip; do arepack $f$f.7z; done