Make garlic-dill dip ahead of time, and chill for at least 2 hours.
Preheat oven to 425°F and line two baking sheets with parchment.
Slice zucchini into 1/4" coins and lay out on paper towels in a single layer. Pat dry to absorb any excess liquid.
Beat egg with water in a small bowl, set aside. In a medium bowl, mix panko breadcrumbs, parmesan and seasonings.
Dip each zucchini slice into the egg, then the breadcrumb mixture. Arrange in a single layer on baking sheets.
Bake 18-20 minutes, or until zucchini is tender and the coating is crispy and golden brown. Serve immediately with dipping sauce.