To a pot of boiling water, add the diced zucchini and cook for 3 minutes. Drain and cool.
In a bowl, combine the parboiled zucchini, mayonnaise, cheddar cheese, eggs, pepper, and garlic powder.
Pour into a greased 1 1/2 quart baking dish.
In a bowl, combine the Panko breadcrumbs with melted butter. Pour breadcrumbs over the top of the casserole.
Bake, uncovered, at 350°F for 35 minutes, or until zucchini is fork tender.
*If freezing the zucchini for this recipe. Take the diced zucchini boil in the water for 3 minutes and then place into a bowl of ice water to stop the cooking. Drain the cooled zucchini and place on a parchment lined baking sheet. Place baking sheet into freezer. The next day bag the zucchini in a couple labeled freezer bags.
*Then at a later date, thaw the zucchini. Drain any excess water. Then continue with the recipe as listed above.
*You can make this recipe without parboiling the zucchini first, but you will need to add more baking time to the casserole.