Put a large pot on medium heat and add 100 grs of the butter. When hot and butter has not been browned, add the zucchini and the garlic. Sauté for few minutes until zucchini get a nice light brown colour. Remove from the pan and discard the garlic.
In the same pot on medium heat add the oil and a minute later add the onions. Sauté for few minutes until translucent and then add the rice stirring to get well coated with the oil. Toss for a minute and then deglaze with the wine.
Allow the wine to reduce by half and the alcohol to be evaporated and then start adding a ladle or two of the vegetable stock at a time, simmer and stir. Continue the same procedure until the rice is cooked to al-dente.
Just before the last ladle and when the rice has some bite in the centre, add the zucchini and the lemon juice. Add the last ladle of stock water and stir. Allow to reduce, you want a creamy but not runny risotto, and add the remaining butter and 60 grs of the parmesan cheese. Season with the salt and pepper, fold in the parsley and remove from heat.
Serve the risotto in a flat dish and sprinkle the remaining parmesan cheese.