1. In a large saucepan, heat the oil over moderate heat. Add the onion, carrots, and 1/2 teaspoon of the salt and cook, stirring occasionally, until the vegetables start to soften, about 5 minutes.
2. Add the garlic, zucchini, yellow squash, broth, tomatoes, and the remaining 1 1/4 teaspoons salt; bring to a simmer. Add the Jerusalem artichokes and return to a simmer. Reduce the heat and simmer, partially covered, until the vegetables are tender, about 10 minutes. Stir in the beans, parsley, pepper, and zest.
Wine Recommendation: The soft nutty flavors and rich texture of pinot gris beautifully complement the earthy sweetness of this tasty soup. Try one from a well-known Alsace producer such as Trimbach, Sparr, Beyer, or Hugel.
Notes: If you don't want to tackle the job of peeling knobby Jerusalem artichokes, just scrub them well with a vegetable brush under running water and leave the peel on.