In a large pot, heat olive oil and butter over medium-high heat. When the butter melts, add in the rice and pasta. Saute for 4 to 5 minutes, then add the shallots and saute 2 minutes more. Add the zucchini and mushrooms and mix to combine. Stir in the stock and bring the mixture to a simmer. Cover and cook for 14 to 16 minutes. Add the tomatoes, parsley, lemon zest and Parmesan. Season with the black pepper and salt, if needed. Transfer to a serving bowl and serve.