Put tomatoes and 4 cups water in a large pot over medium-high heat. Add broth base, onion, carrots, celery, garlic, black pepper, dried basil, and dried oregano. Stir, cover with lid, and bring to a simmer. Reduce heat to medium. Let cook for 25 minutes.
Add orzo and zucchini, cover, and cook an additional 10 to 15 minutes, until vegetables are tender. If needed, add additional water to replace moisture lost in evaporation. Soup should be thick.
Nutritional information per serving: 132 calories, 3 g protein, 1 g fat, 0 g saturated fat, 28 g carbohydrate, 4 g fiber, 4 g sugar, 190mg sodium.