For months, Senator Elizabeth Warren of Massachusetts has made “big, structural change,” the rallying cry of her presidential campaign. And when it comes to the tech sector, that has meant taking square aim at giant companies like Facebook — companies she says have become so large that they are stifling competition.

Ms. Warren rolled out a proposal to break up Facebook, Amazon and other tech giants in March. To ensure that tech workers got her message, her campaign paid for a billboard near a major transit station in San Francisco. It read “Break Up Big Tech,” in capital letters.

On Tuesday, nearly seven months after Ms. Warren first unveiled her plan, The Verge offered a window into what Mark Zuckerberg, Facebook’s chief executive, thinks about it. In leaked audio recordings of open meetings with employees this summer, Mr. Zuckerberg can be heard saying that the company would sue if Ms. Warren were to enact the plan as president.

“If she gets elected president, then I would bet that we will have a legal challenge, and I would bet that we will win the legal challenge,” he said.