The toughest leadership task for Dieter Zetsche, chairman of the board of management of Daimler AG and head of Mercedes-Benz Cars, was engineering last year’s breakup of Daimler and Chrysler. Zetsche lived in Detroit for five years while trying to spearhead a turnaround at Chrysler — an effort that included appearances in Chrysler’s humorous “Ask Dr. Z” television commercials, where his signature walrus mustache made him a minor celebrity. Then, in 2006, after he became CEO of the German parent company, he faced a new set of leadership responsibilities. “My five years as CEO of Chrysler were personally among the very best of my life, but I still had to put my feelings aside and view the situation objectively from a business perspective,” said Zetsche during a recent Wharton Leadership Lecture. In 1998, Chrysler and Daimler announced they would join forces in a $37 billion stock swap, creating a new company that had 442,000 employees and a market capitalization of nearly $100 billion.…