Zing Wireless Inc., an online market research firm that operates under the name GoZing, has been sold to a Wilton, Conn.-based company in a similar business. The purchase price was $30 million in cash. Greenfield Online Inc., which also provides panels of survey takers for marketers and others, said the acquisition will create one of the largest opt-in Internet-only panels. GoZing, based in Encino, will discontinue its cellular reseller business, which the companies said represented about 10 percent of GoZing’s $13 million in revenues. GoZing’s three senior executives, Matthew Dusig, who had been president, Gregg Lavin, who was CEO and Lance Suder, COO, will remain with the company. Dusig becomes senior vice president corporate strategy. Lavin becomes senior vice president online marketing. And Suder becomes senior vice president of West Coast operations.