Heat olive oil in a stock pot over medium-high heat. Add the rice and stir until thoroughly coated and opaque, about 3 minutes. Add the onion and garlic, and cook until softened, about 2 minutes.
Add the white wine and cook until reduced by half and the alcohol smell is completely gone, about 2 minutes.
Add one cup of the stock and cook, stirring, until the liquid is absorbed. Continue stirring and continue to add the stock, one cup at a time, waiting until the liquid is absorbed each time before adding more. Fold in the zucchini after about the 5th cup of stock and once all stock has been added, continue to cook until the rice is tender and creamy but still al dente, 10-12 minutes.
Remove from the heat and add the lemon juice and zest.
Stir in Parmesan cheese and parsley. Give a quick stir to partially melt the cheese.
Add salt and freshly ground pepper, to taste.
Plate the risotto and drizzle with more olive oil, if desired. Top with additional Parmessan.
This recipe makes 6 servings as a side dish or 4 as a meatless main dish.