In a saucepan of boiling salted water, cook pasta according to package instructions. Drain, reserving 1/2 cup cooking liquid.
In a large bowl, toss together pasta, ricotta, lemon zest, salt, pepper, and half of the reserved cooking liquid.
Meanwhile, quarter each zucchini lengthwise. With knife, cut away core; cut on bias into slices.
In a skillet, heat oil over medium-high heat; saute zucchini until tender, about 5 minutes. Add to pasta, along with mint, green onion, lemon juice, and enough cooking liquid for desired creaminess, tossing to coat.