It is likely that your listing was submitted to Yahoo! Real Estate via Zillow through one of their bulk listings providers. This is probably a company that you have a relationship with (your website provider, your virtual tour provider, or another company that you advertise with).

Unfortunately, Yahoo! Real Estate cannot remove listings on an individual basis. If you don't want a resale home listing to appear on Yahoo! Real Estate, please contact the company directly and ask them to remove it from their feed to Zillow which would in turn remove it from Yahoo! Real Estate