Cook the quinoa according to the directions on the package.
Place all the ingredients for the vinaigrette in a blender and blend until smooth.
Heat 1 tablespoon olive oil in a skillet over medium heat for 1-2 minutes. Test the oil with a piece of zucchini – once it sizzles upon contact, add the rest of the zucchini and sauté until softened (but not squishy), about 2 minutes. Transfer the zucchini to a plate or bowl. Add the corn to the skillet and sauté until tender (about 8-10 minutes for fresh corn, 1-2 minutes for frozen or canned). If you are using frozen corn, heat it in the microwave and drain any excess liquid before adding it to the skillet.
In a large bowl, combine the quinoa, zucchini, corn, diced peach, and vinaigrette. Stir in half of the cotija, and sprinkle the remaining half on top, along with the chopped green onions.