Preheat the oven to 375°F (190°C). Position a rack in the center and line an 8 x 8-inch (20 x 20 cm) baking dish with parchment paper, leaving enough overhang to lift out the casserole after baking. Allow approximately 10 minutes for preheating, or until the oven reaches the correct temperature.

Coarsely grate the zucchini using the large holes of a box grater. Measure 2 cups (250 g), then transfer the grated zucchini to the center of a clean kitchen towel. Gather the towel and squeeze firmly until excess liquid stops dripping readily. The zucchini should feel damp but not dripping wet. This step limits excess moisture in the batter.

In the large mixing bowl, whisk together the yellow cornmeal, all-purpose flour, baking powder, baking soda, salt, and black pepper for approximately 30 seconds. Continue until the mixture looks evenly blended and no visible pockets of leavening remain. Even distribution helps prevent uneven rising.

In the medium mixing bowl, whisk the eggs, buttermilk, melted and slightly cooled butter, and honey for 1 minute, or until the mixture looks smooth and uniformly combined. The butter should be fluid but not hot, which helps prevent premature egg coagulation.

Add the drained zucchini, sweet corn kernels, shredded cheddar, and sliced scallions to the wet mixture. Stir gently for approximately 30 seconds, until the vegetables and cheese are evenly distributed. Separate any large clumps of zucchini so the vegetables bake evenly.

Pour the wet mixture into the dry ingredients: Fold with a spatula for approximately 30–60 seconds, stopping when no dry flour patches remain. The batter should look thick, moist, and slightly lumpy, with visible zucchini and corn throughout. Avoid excessive mixing, which develops gluten and can make the casserole tough.

Transfer the batter to the prepared 8 x 8-inch (20 x 20 cm) baking dish. Spread it evenly with the spatula, leveling the surface and filling the corners. The mixture should form an even layer without large air pockets, helping the center bake at the same rate as the edges.

Place the baking dish on the center oven rack and bake at 375°F (190°C) for 35–40 minutes. The casserole should have a golden-brown top, lightly browned edges, and a center that feels set when gently pressed. Insert a toothpick into the center; it should come out without wet batter, although a few moist crumbs or melted cheese are normal. If necessary, continue baking briefly until the center is fully set.

Remove the baking dish from the oven and place it on a wire cooling rack. Let the casserole rest for 10 minutes so steam redistributes and the starches finish setting. The surface should become firmer and easier to cut. Lift it out using the parchment paper, divide into 8 portions, and serve warm.