I have been noticing that this has been a frequent inquiry, so for those who don't know, here's how:
Now that you packed the song to a SMZIP package, you have been wondering how can you convert this to a ZIP.
The SMZIP format is actually a ZIP file that contains the automated instructions so that it can be installed to Stepmania, hence, to convert a SMZIP file to a ZIP file...
Simply rename the SMZIP extension to ZIP so it can be a ZIP file
to see the file extension just in case you can't see it,
in your windows Explorer, choose Tools then Folder Options
Choose the View tab and uncheck "Hide extensions for known file types"
now you can freely rename the file
cheers