Dice the meat and fry in a pan with hot oil. Season with salt and pepper. Deglaze with stock and cook for about 45 minutes. Clean, wash and dice the zucchini. Peel onions and cut into slices.
Add the vegetables to the meat about 20 minutes before the end of the cooking time. Stir yoghurt and starch until smooth. Season to taste with lemon juice and mustard and add to the vegetable goulash. Bring to the boil briefly and season with salt and pepper.
Wash the parsley, cut into strips and sprinkle over the vegetable goulash. Serve in the pan.