First, put the eggplant slices in a colander and sprinkle with salt to rid them of their bitterness. After half an hour, rinse and pat dry.
Lightly fry the eggplant, onion, garlic, green zucchini and red pepper in a pan. Put the contents of the pan in the slow cooker and add the yellow zucchini, tomatoes, olive oil, white wine, sugar and red wine vinegar. Put the lid on and cook for 4 to 6 hours on low or 2 to 3 hours on high.