Combine eggplant, bell peppers, onion, tomatoes with juices, chickpeas, garlic, oil, basil, oregano, salt and pepper in a 6-quart slow cooker.
Cover and cook on low for 5 hours until eggplant is mostly tender.
Stir in zucchini, cover and cook on low for 1 1/2 to 2 hours more until all vegetables are tender but still hold pieces. Stir in vinegar.
Bring 1 1/4 cups water to a boil in a small saucepan. Stir in couscous, cover, remove from heat and let stand for 10 minutes.
Fluff couscous with a fork and divide among 6 shallow bowls.
Spoon ratatouille and chickpeas over the couscous, including a little tomato cooking liquid in each serving.