It sounds as if the zip file has the "hidden" attribute. You can set Windows* to show files with that attribute, or not to. If you right-click on the filename in your search results, then click on Properties, you should be able to see its attributes and perhaps change them.

If you can see the file in your search results, is that enough access for your purposes or do you need it to show up somewhere else too? Would creating a "shortcut" to it work?

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*My experience is limited to Windows XP and 98. Other Windows versions may work differently from how I've described.