Preheat grill to medium-high heat. Cut zucchini into long spears by cutting in half lengthwise and then each half cut again. Brush with olive oil and generously season with salt, pepper and garlic powder.
Place zucchini on heated grill and allow to cook for about 2 minutes on each side or until cooked but not overly soft so that it doesn't become mushy and water logged. Remove from grill, cool for several minutes and then cut into bite sized pieces. If grilling the corn as well, brush lightly with olive oil on all sides and the cook for about 15 minutes, turning slightly every 2-3 minutes.
Cook pasta al dente according to package. Drain water and run under cold water.
In a large bowl, combine pasta, zucchini, corn, tomatoes, basil, and onion. Toss to combine.
Add parmesan, garlic, lemon juice, lemon zest, olive oil, vinegar, salt and pepper and toss. If it seems dry, add in more olive oil. If you prep this recipe in advance, toss a bit more olive oil in before serving to add back any moisture that has been absorbed.