To install it, download Zip.qlgenerator.zip first. Unzip the file. Copy or drag the Zip.generator to /Library/QuickLook/, make a QuickLook folder if you don't have one.
Then restart the Finder. Here I learned a new tip to restart Finder:
- locate the Finder in Dock,
- press Ctrl+Opt+click or Opt+right click;
- you will see a list of context menu, and select Relaunch.
It will relaunch Finder. Now you should be able to view the content of a zip file.