Preheat oven to 400F (200C) and grease a 9 x 13 baking dish with avocado or olive oil.
Trim the zucchini, cut in half lengthwise, and scoop out the flesh and seeds with a small spoon or fruit baller/fruit scoop. Divide and reserve half the zucchini flesh for filling. Squeeze out excess water and finely chop before adding to the sauce.
Place zucchini halves cut-side up on a baking sheet. Drizzle with olive oil, season with salt and pepper, and bake for 15 minutes until slightly softened for further baking with filling later. Set aside.
Saute onion in a skillet over medium heat until softened.
Add tomatoes, chicken, reserved zucchini flesh, Italian herbs or oregano, and garlic powder.
Saute for 2 minutes more and stir in the cream.
Add Parmesan, simmer for 2-3 minutes until slightly thickened.
Taste and adjust seasoning with salt and pepper if necessary.
Once the zucchinis are halfway softened, evenly distribute the chicken stuffing among them.
Sprinkle with cheese on top and bake for another 10 minutes until cheese is melted.