This is currently not possible, as our RSS to GeoRSS converter does not yet support Dutch.
The feed has as zip element within the item element. Unfortunately this is not part of the RSS2.0 specification :
http://blogs.law.harvard.edu/tech/rss#hrelementsOfLtitemgt
If you are the developer of the feed http://allestekoop.com/rss.php, then you can add the zip and country information using GeoRSS and we push the adoption of our proposal.