Well, with little few-worded prods from you guys I was able to solve the problem.
The rss2html.php uses a document template to parse the contents of the feed into. Naturally, the template variable in the script is called $template. I don't have to tell you what happens when the $template variable contains something other than what zen-cart put in there.
After renaming all instances of "$template" to "$rsstemplate" (including the external variable [$rssTEMPLATE] set in your code used to invoke the script), it worked as advertised.
Basically you can create any number of document HTML templates, and place these lines of PHP code anywhere in your site to display a feed where ever you want it to be.
<?php
$XMLFILE = "http://URL path/someRSS.xml ";
$rssTEMPLATE = "includes/languages/english/html_includes/CUSTOM/your_HTML_Template.html";
$MAXITEMS = "1";
$NOFUTUREITEMS = "1";
include("rss2html.php");
?>
For more information, I'll be glad to help out anyone who asks.
In the mean time, :cheers: