| Bring first 7 ingredients to a boil in a heavy nonreactive saucepan. Reduce heat to medium low, and simmer, uncovered, about 15 minutes, until onion is softened. Stir in zucchini and tomatoes. When mixture begins to simmer, add fish. Gently fold into broth and simmer 2 minutes, until fish turns opaque. Stir in vinegar, butter, cilantro and salt to taste. Remove from heat and serve. |