Website Zillow will power all for-sale listings on Yahoo! Real Estate in a new partnership that will to go into effect later this year. The deal combines the second and third most trafficked real estate websites. Homebuyers using Yahoo! Real Estate will continue to search for homes by geography, pricing and other criteria, but will have access to the more than 4m listings from Zillow. Once the deal is fully implemented, real estate agents and brokers who advertise and place listings on both sites will be offered a new package to be placed on both. Listings will automatically be placed on both, which, according to Zillow will reduce the amount of data feeds for brokers and agents currently using both. The new deal also gives homeowners the chance to purchase “for sale by owner” listings, which can appear on both sites. Yahoo! and Zillow have partnered before. Through a deal in 2006, Yahoo! Real Estate began using the Zillow automated valuation model (AVM) branded as “Zestimates” to value more than 72m homes on its site. But a report in the winter 2010 issue of The Appraisal Journal, which compared a sample of the Zillow valuations to Multiple Listing Service (MLS) sales data, found that Zillow overestimated the home values as often as the owners. Zillow called the report, “misleading.” In November 2009, another Internet giant, Google, partnered with Mortech, a software developer, to design a new searchable mortgage-pricing tool for home shoppers. Spencer Rascoff, COO of Zillow, said the latest partnership with Yahoo! Real Estate will give advertising agents and brokers the ability to reach one of the largest homebuyer audiences on the Web. Steve Schultz, head of Yahoo! Real Estate, agreed. “This partnership enables us together to better serve the advertising needs of real estate agents and brokers and bring highly scalable solutions to the market,” Schultz said. Write to Jon Prior.