Step 1Heat the oven to 375 degrees with a rack positioned in the center. Butter a 9-inch casserole.
Step 2Place the corn and zucchini in a bowl and toss with the flour to evenly cover. Spread into the casserole.
Step 3Wipe the bowl clean and combine the eggs and yolks and whisk briefly. Add the cream and salt and whisk until fully incorporated. Pour over the vegetables.
Step 4Bake about 1 hour, until lightly browned on top; it should feel like a firm pillow. Allow to cool 10 to 15 minutes before serving.