Preheat the grill for medium high heat. That means filling the charcoal chimney 3/4 to full with coals. Add lit charcoal to the grill and spread it in one even layer. Let the grill preheat for a few minutes and place a large cast iron skillet on the grill over direct heat and let it preheat.
While everything is preheating, dice vegetables and prepare other ingredients.
When the skillet is hot, add oil, onion, and peppers. Mix and let them cook until softened. Stir them around from time to time.
Pour in balsamic vinegar and let it simmer vinegar for a few minutes.
Add sausage and zucchini and season everything with salt, garlic powder, and crushed red pepper flakes.
Mix well and cook until vegetables and sausage are done. Just make sure to stir every few minutes.
Notes
Disclaimer: Nutrition information shown is not guaranteed to be 100% accurate as most ingredients and brands have a slight variation.