To prepare an air fryer zucchini yellow squash and onions recipe, you'll need: Zucchini, Yellow Squash, Onion, Salt, Pepper, and Olive Oil. In a large skillet, heat the oil over medium-high heat. Add the zucchini and cook, stirring frequently, until the squash is soft and tender, about 5 minutes. Remove from the heat and add the onion and salt. Toss to coat.