Heat the oil in a pot over medium heat. Stir in risoni and cook 2 minutes until golden. Stir in garlic, zucchini and carrot and cook 2 minutes. Pour in the broth and mix in lemon zest. Bring to a boil. Reduce heat to low and simmer 10 minutes or until liquid has been absorbed and risoni is tender. Season with thyme and top with Parmesan to serve.