WASHINGTON — Five years ago, Jeffrey D. Zients was the head of the Obama administration’s National Economic Council, working to push across the finish line a federal rule that would prevent financial advisers from taking advantage of retirees. He won praise from progressives for fending off fierce resistance from Wall Street and for fighting for consumer protections.These days, Mr. Zients is a co-chairman of President-elect Joseph R. Biden Jr.’s transition team who is being watched warily by members of Democratic Party’s left wing. Progressive advocacy groups such as the Revolving Door Project and Justice Democrats, concerned that …
