Dining, creativity, surfing, and roots music are on Guild Hall’s cultural menu this week, starting Sunday morning, when “Stirring the Pot,” a series of culinary-centric conversations, will feature Tim and Nina Zagat, who founded the Zagat Survey 40 years ago. Initially a collection of reviews of New York City restaurants by diners, the survey at its height included 70 cities. In 2011, Google acquired it for $125 million.