Combine the marinade and set aside.Cut and cube the sirloin and add it to the marinade.Marinate for 2 to 3 hours.Preheat the oven to broil.Cut the green pepper into squares and the zucchini into small wheels. Arrange the meat on skewers and the green pepper,zucchini,onions and mushrooms on separate skewers.Broil the meat on a rack 10 cm from the heat.Brush with marinade and turn every 2 or 3 minutes.The meat should cook for about 10 minutes and the vegetables for about 5 minutes.