Antonio Weiss has an innate understanding of how to use diplomacy to bridge cultural divides. The son of a musicology professor from Trieste, Italy, and his American wife, a music teacher, Weiss grew up in New York City, spent his childhood summers in Italy and learned how to be at home on two continents. That trait is crucial for the Paris-based banker, who was named global head of M&A at Lazard in March after leading the bank in one of its biggest deals ever.

A longtime adviser to InBev CEO Carlos Brito, Weiss, 42, helped the Belgian brewer pull off its $52 billion acquisition of St. Louis–based Anheuser-Busch Cos. last year. The deal was hardly a foregone conclusion. Anheuser-Busch is an American icon that controls more than half of the U.S. beer market, and...