I don't believe this is possible without using the API / JavaScript. Reading through the available query string parameters, there are none which allow you to specify a kml/kmz input file separate from just the q= query string variable. It looks like the staticmaps ( URL for multiple markers in Google Maps ) feature may include the ability for multiple markers though if this could serve your purpose. you will need to pass the KML as part of the query string though, something like:
?q=http://code.google.com/apis/kml/documentation/KML_Samples.kml&markers=-134,68,0
Good luck!