In 5-quart Dutch oven cook leeks, celery, and garlic in oil over medium heat for 10 minutes or until beginning to brown. Stir in broth, undrained tomatoes, kale, zucchini, 1.4 teaspoon each salt and black pepper. Bring to boiling; reduce heat. Simmer, covered, 5 minutes, stirring once. Reserve a few spinach leaves; stir in remaining spinach, parsley, and vinegar. Top with reserved spinach leaves. Makes 8 side-dish servings.