Mark Zuckerberg and Elizabeth Warren are clashing over her plan to break up the tech titans — a war of words that could test the limits of Silicon Valley’s liberal leanings. The Facebook CEO was caught railing against Warren and her proposal to smash the internet’s virtual monopolies — Facebook, Google, Amazon and Apple — in leaked audio of open meetings with employees this summer released Tuesday by The Verge. “You have someone like Elizabeth Warren who thinks that the right answer is to break up the companies … if she gets elected president, then I would bet that we...