Soak a dozen 12-inch bamboo skewers in warm water.
Beef kabobs. Combine steak and dressing in a resealable plastic bag. Refrigerate to marinate, 30 minutes. Place peppers and onion in one side of a microwave-safe dish. Set aside.
Chicken kabobs. Combine chicken and dressing in a resealable plastic bag. Refrigerate to marinate, 30 minutes. Add zucchini and peppers to dish with peppers and onion. Cover with plastic, venting one corner. Microwave 2 minutes to soften vegetables.
Heat gas grill to medium-high or coals in charcoal grill to medium hot. Begin threading kabobs. Beef Kabobs: Thread 1 beef cube, 1 piece onion, 1 tomato and 1 pepper piece onto a skewer. Continue threading until you have filled a total of 6 skewers. Chicken Kabobs: Thread chicken, pepper piece, zucchini and a different color pepper piece onto a skewer. Continue threading to fill 6 skewers.
Grill chicken kabobs 4 minutes per side, until cooked through, beef kabobs for 3 minutes per side until cooked through. Serve both kabobs with dipping sauce.