Mix ground chicken, breadcrumbs, yellow onion, parmesan cheese, dijon, garlic and salt and pepper together in a large bowl.
Preheat oven to broil on high. Heat a large heat safe skillet with olive oil over med-high heat. Divide meat mixture into 18 round balls, then cook for 10-12 minutes, tossing often, until browned and cooked through.
Meanwhile, heat a large pot of water on the stove with a pinch of salt until boiling, then add pasta. Cook for 10 minutes until al dente, adding zucchini in last 2 minutes of cook time before draining and setting aside.
Pour pasta sauce in skillet then top with cheese. Broil for 1-2 minutes until cheese has melted, watching closely so it doesn't burn. Remove from oven, garnish with fresh basil or parsley, then serve 3 meatballs overtop of pasta and zucchini. Enjoy!