Heat olive oil in a large skillet over medium heat. Add zucchini and garlic; cook and stir until lightly browned. Off heat, set aside.

Combine tomatoes, onion, and chile pepper in a blender or the bowl of a food processor; pulse until puréed, leaving a few small chunks.

Combine tomato purée and vegetable broth in a large pot; season with tarragon, dill, salt, and black pepper. Bring to a boil, reduce heat to low, and stir in zucchini-garlic mixture. Cover; cook for 45 minutes.