In a food processor, combine the garlic, pine nuts, basil, yeast , lemon zest and lemon juice. Pulse until ground to a fine paste, about 1 minute. With the machine running, slowly drizzle in the olive oil until the desired consistency is reached. Season with salt and pepper.
Preheat the oven to 425 F for the zucchini, and have ready a large rimmed baking sheet lined with parchment paper.
Warm the vegetable broth in a saucepan. Keep it warm on the lowest setting possible as you prepare the risotto.
Preheat a heavy-bottomed 4 quart pot over medium heat. Sauté the onion in oil and a pinch of salt until translucent, 4 to 5 minutes.
Add the rice and use a wooden spoon to stir and coat with oil. Add the white wine and stir occasionally, until wine is mostly absorbed, 4 minutes or so. Add a few dashes of salt and pepper. Reduce heat to medium low.
Add the broth by the cupful, stirring the risotto after each addition until the broth is mostly absorbed (6 to 8 minutes). After 2 cupfuls, add about half of the pesto and stir well, then continue to cook, adding broth by the cupful, stirring, and letting the liquid absorb.
At some point in there, your oven will be preheated. Toss the zucchini with oil, salt, pepper and garlic. Roast for about 6 minutes on each side, or until softened and lightly browned. Remove from oven and set aside.
With your last addition of broth, add the remainder of the pesto. Taste for salt and add the other 1/4 teaspoon if needed. Risotto is ready when the rice is chewy but still firm, and the sauce is very creamy. For a firmer risotto, just cook a few minutes extra to absorb more of the liquid.
To serve: scoop risotto into each bowl, and top with zucchini. Drizzle with extra pesto and garnish with a few toasted pine nuts.