Cut the kernels off 1 ear of corn. Grate 1 small zucchini, then squeeze dry in a kitchen towel. Toss the corn, zucchini, 1/2 cup sliced cherry tomatoes, 2 sliced scallions, 1/2 teaspoon kosher salt and a few grinds of pepper in a large bowl. Add 2 cups grated Colby jack cheese; toss. Divide among 4 slices white bread and top each with another slice of bread; press to adhere. Lightly butter the outsides of the sandwiches. Grill over medium-low heat, rotating as needed, until well marked and the cheese melts, 3 to 5 minutes per side.