Why is unzipped directory much smaller (4.0 K) than zipped (73.0 G)?
The size of a directory as shown in your screenshot isn't the sum of the size of the contents, it is the size of the meta-data associated with the directory - file names, etc.
https://unix.stackexchange.com/questions/55/what-does-size-of-a-directory-mean-in-output-of-ls-l-command
To find out how much space the directory contents are using, you can use
du -sh /path/to/directory