Steam broccoli on stove top or in microwave until just tender. Drain and pat dry and then set aside for later.
In a large skillet over medium heat, warm olive oil. Once it is heated, combine garlic, pinch of red pepper flakes (use up to ¼ teaspoon depending on how much heat you like), and onions. Cook for 2-3 minutes or until onions become translucent. Add in remaining vegetables (with the exception of the zoodles and broccoli) and lightly season with salt and pepper to taste. You can always add more seasoning later. Cook for 3-4 minutes or until bell pepper is soft.
Add zucchini and sweet potato noodles, lemon juice and parsley, stirring as you cook for another 3 minutes until noodles have cooked to al dente.
Add in broccoli and Parmesan cheese and toss completely to spread the cheese.
Plate into bowls or plates and top with more Parmesan cheese and a sprig of parsley, to garnish.