Lightly salt the eggplant slices and place on paper towel to drain for about 30 minutes. Rinse and pat dry.
Slice the zucchini thickly and set them aside.
Pour 3 tablespoons of the olive oil into a large frying pan and when hot, lightly brown the onions, peppers and zucchini slices.
Remove the vegetables to a casserole and add the eggplant slices to the frying pan or saucepan.
Cook to brown both sides lightly and place in the casserole with the other vegetables. Add extra oil as needed while frying the vegetables.
Add the garlic and tomatoes to the oil and cook for 1 minute. Add the garlic and tomatoes to the rest of the vegetables with the remaining olive oil in the frying pan.
Add basil, salt, pepper and wine and bring to the boil over moderate heat.
Cover and reduce to simmering. If the vegetables need moisture during cooking, add a little more wine.
When the vegetables are tender, remove them from the casserole to a serving dish and rapidly boil any remaining liquid in the pan to reduce to about 2 tablespoons. Pour over the ratatouille to serve.