Warner Bros. Discovery CEO David Zaslav brought out the big guns during his address to the new company at its first global town hall for employees Thursday.The newly merged company brought out its most famous employee, Oprah Winfrey, to moderate the event and to help introduce Zaslav to Hollywood.Winfrey is a longtime supporter of the media mogul, who has championed the Oprah Winfrey Network (OWN) — a cable channel jointly jointed by Warner Bros. Discovery and Harpo Studio — alongside her since its launch in 2011.