Elt 1T of butter in a heavy casserole pot over medium low heat. Meanwhile put the stock in a pan over low heat. Add garlic, pepper flakes (or chile) and onion and sauté until soft, about 5 minutes - don't let it brown. Add zucchini, lemon zest, a few grinds of fresh pepper and 1/2t salt. This will draw the water out of the zucchini. Turn the heat up to medium and cook until the water comes out of the zucchini and evaporates again, stirring regularly.
Move zucchini to the sides of pan and add another tablespoon of butter, allow it to melt and start sizzling. Add the rice and stir it all together allowing the rice to absorb the moisture of the butter and vegetables. Cook, stirring constantly for about a minute, don't let it stick. Add the wine and continue stirring until absorbed, about 2 minutes. Add stock by the ladle until it has been absorbed stirring constantly. After your first addition of stock has been absorbed add 1T of lemon juice with the next round of stock.
When the rice is almost done but just slightly al dente take the heat off the bottom of the pot and stir in remaining butter, cheese and parsley. Taste for seasoning. Add another tablespoon of lemon juice and stir into the risotto.