AT&T, owner of HBO and Warner Bros studios, and Discovery, home to lifestyle TV networks such as HGTV and TLC, said on Monday they will combine their content assets to create a standalone global entertainment and media business. Discovery President and Chief Executive David Zaslav will lead the proposed new company, which brings together one of Hollywood’s most powerful studios, including the Harry Potter and Batman franchises, and Discovery’s stable of unscripted home, cooking and nature and science shows. The new company, whose name will be disclosed by next week, will be 71 percent owned by AT&T’s shareholders and 29 percent by Discovery’s. Other details, including the future of WarnerMedia CEO Jason Kilar in the new company and how the combined properties and services will be arrange have yet to be worked out, executives said on a call with reporters after the deal was announced. The move marks the unwinding …