Preheat your oven to 425°F. Line large rimmed baking sheets with unbleached parchment paper and set them aside.
Slice the zucchini (or yellow squash) into 1/4-inch thick rounds and place them in a large bowl. If you have a mandolin slicer, set it to the largest slicing setting. Add the flour to the bowl of zucchini slices and toss to coat completely, prying open any slices that have stuck together.
Place the eggs and milk, in another large, flat bowl, and whisk to combine. Place the breadcrumbs, Parmigiano-Reggiano cheese, garlic powder and salt in a large, flat bowl, beside the egg mixture. Place the lined baking sheets next to the breadcrumb mixture.
Dip each slice of zucchini in the egg mixture, allow all of the excess egg to drip back into the bowl, and the press both sides into the breadcrumb mixture. Place each slice on the prepared baking sheets, side by side. Place in the center of the preheated oven and bake until soft to the touch & golden brown, about 15 minutes. The zucchini slices can be enjoyed just like this, with some tomato sauce for dipping.
To make a more traditional eggplant-parm-type dish, reduce your oven temperature to 350°F. Cover the bottom of a 9-inch x 12-inch baking dish with about 1/2 cup tomato sauce, then place baked zucchini slices on top of the sauce in a single layer, cover each slice with sauce, and top with shredded cheese. Repeat the zucchini slice, tomato sauce then cheese, layering the slices on top of one another, until you reach the top of your dish, finishing with a layer of shredded cheese.
Place in the center of the preheated oven and bake for about 10 minutes, or until the cheese is melted and the sauce is bubbling.