Place the quinoa in a fine-mesh strainer and rinse it thoroughly under cool running water.
Add the rinsed quinoa, water or broth, and salt to a medium saucepan. Bring the mixture to a boil over medium-high heat.
Reduce the heat to low, cover, and simmer for about 15 minutes, or until the liquid has been absorbed.
Remove the saucepan from the heat and let the quinoa rest, covered, for 5 minutes. Fluff it gently with a fork, then spread it on a baking sheet or large plate to cool.
Heat 1 tablespoon of olive oil in a large skillet over medium heat.
Add the diced zucchini and corn. Cook for 5–7 minutes, stirring occasionally, until the zucchini is tender and the corn begins to turn golden. Remove the skillet from the heat and allow the vegetables to cool slightly.
To make the dressing, add the olive oil, lemon juice, honey, garlic, Dijon mustard, salt, and black pepper to a small bowl or jar. Whisk or shake until combined.
Add the cooled quinoa, zucchini, corn, cherry tomatoes, basil, and green onions to a large serving bowl.
Pour the dressing over the salad and toss gently until everything is evenly coated.
Taste and adjust the salt, pepper, or lemon juice as needed. Serve immediately or refrigerate until ready to eat.