MILAN, Dec 16 (Reuters) - Italian luxury group Ermengildo Zegna will debut on the New York Stock Exchange on Dec. 20 after a U.S. investment vehicle launched by private equity firm Investindustrial gave its green light to a combination of the two, a regulatory filing showed. Family-owned Zegna said in July it would list in New York by the end of the year by combining with blank check firm Investindustrial Acquisition Corp (IIAC), in a move that was expected to give the menswear company an enterprise value of $3.2 billion and help it expand in Asia and the United States. read more