When your computer indexes a ZIM file it is stored somewhere in your windows /Users folder. You can download the 'portable version' of your ZIM file from download.kiwix.org that already includes an index that works from multiple computers. Download those and extract the portable versions on top of each other to have all the ZIM files indexed and ready in yoru portable Kiwix.

If you want to use your own indexes its a bit harder, but here we go:

Move the index file, Zim file and XML configuration file inside the Kiwix installation folder for example to: c:\kiwix\data

The index file is stored in the /data/index path, the index you have created is in a local folder somewhere in your /Users folder so you have to search there for the Kiwix settings folder and move the index to the c:\kiwix\data folder.

Take a look at /data/library in your user folder.

There are many XML configuration files there. You can open these with Notepad. Search for 'indexPath' and take a look at what is says there. Correct the path to a relative path like so:

indexPath = '../index/wikibooks_nl_all_2014-12.idx'

also make sure the 'path' points to a relative folder where your ZIM is.

Correct that to point to the locations where the index and ZIM files are.

You have now created your own portable Kiwix.