ZipRealty added a 16th brokerage to its “Powered by Zip” referral network in April, but net revenue was down 4 percent during the first quarter from a year ago, to $15.4 million, the company said today. The Emeryville, Calif.-based brokerage — ranked by Real Trends as the nation’s 31st-largest brokerage by 2012 closed sales volume — posted a $2.2 million net loss for the quarter, compared to a $3.1 million loss a year ago. At the end of March, ZipRealty had 1,576 agents working out of company-owned offices in 19 markets and, and was providing its technology to nearly 500 additional agents in “Powered by Zip” referral markets. St. Louis-based Coldwell Banker Gundaker is the latest addition to the Powered by Zip network, in which participating brokerages provide IDX listings to ZipRealty.com and receive leads and customer relationship management tools. Source: sec.gov.