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.