Clean, wash and slice the aubergine. Sauté briefly all around in hot olive oil. Take out, drain and let cool. Clean and wash the rest of the vegetables as well.
Cut the peppers and tomatoes into large cubes and the zucchini into slices. Put everything, including the eggplant, in a bowl and mix well. For the marinade, peel and finely chop the garlic or press it through the garlic press.
Mix with the mustard. Add vinegar and finally add the oil drop by drop. Season to taste with salt, pepper and sugar. Crumble the feta cheese into small cubes and carefully fold into the salad.
Pour the marinade over the salad, mix in lightly and leave to stand in the refrigerator for some time. Finally, sprinkle with coarse black pepper.