In a 2.5 quart sauce pot (or larger), heat olive oil and add zucchini, onion, red pepper flakes, salt and pepper. Cook until the zucchini browns a bit, about 10 minutes. Try to avoid stirring the mixture more than once or twice, so the zucchini is able to brown.
Add garlic and diced chicken sausage and cook for 2-3 minutes.
Add chicken broth to the pot and bring to a boil. Add tortellini, stir to cover as much of the tortellini with the liquid as possible. Lower the heat to medium, cover with a lid, and cook for about 4 minutes, until the pasta is tender.
Remove from heat and stir in the pesto and juice from half of a lemon. Add the tomatoes and Mozzarella pearls and gently stir to combine.
Serve by topping with parmesan cheese.