You first have to understand that basics of how this hack works.

It works by running ALL sites from the SAME code. For example, I have http://www.bfsb.dk pointing to the same physical location as xoops.web-udvikling.dk, so it is the SAME index.php that is accessed.

You can do it with subfolders on Apache with the ALIAS directive in the apache's httpd.conf file, making an alias for the (non-existing) subfolder to point to the root.

In your example, you would

1) install XOOPS on 127.0.0.1
2) install site administration on this site.
3) Create a new site in the site administration module, with the URL http://127.0.0.1/humor and the prefix zxcvb
4) Create an ALIAS in your apache's httpd.conf file
5) Restart apache
6) access 127.0.0.1/humor and start configuring this site. The first thing I do is to change the name of the site in the site's normal XOOPS general preferences and then I uninstall the Site admin module from this site to avoid confusion

To install a module and share it with other sites do this:
1) Install module on all the sites that should have the module - include the "base" site (127.0.0.1/ in your case)
2) Edit each site in the "base" site's Site Administration module to share the new module's tables

To uninstall a shared module from a subsite do this:
1) Edit the subsite in the "base" site's Site Administration and set the module's tables to not be shared anymore
2) Uninstall the module on the subsite

Especially the uninstallation procedure can cause problems if you don't un-share the tables first (since the tables will then be removed by the uninstallation - but all the other subsites will still have references to the module in their database tables)