Heat a grill to 350 degrees F. (Or preheat the oven on its lowest temperature setting.)
Make a large aluminum foil pouch and add the tomatoes, onions, garlic, zucchini, bell peppers, eggplant, Italian seasoning, paprika, a pinch of salt and a drizzle of olive oil. Gently toss together and then tightly close the aluminum pouch.
Place the pouch over the indirect heat area of your grill (or in the oven on the lowest setting). Cook, picking up the pouch with tongs and tossing 2 to 3 times while cooking, until everything sounds soft inside, anywhere from 30 to 50 minutes depending on the cooking method.
Pour the aluminum pouch contents into a large bowl. Add the lemon zest and a spritz of lemon juice and toss. Taste and season with salt and a few grinds of black pepper. Sprinkle over the parsley and serve.