Shred zucchini and 1 carrot; slice green bell pepper into rings. Set all aside.
On 4 slices of bread, add a few spoonfuls of marinara sauce. Top with bell pepper rings, shredded zucchini, shredded carrot, and cheese.
Top with remaining 4 slices of bread.
Spray a large sauté pan with cooking spray and heat over medium-high heat.
Add sandwiches, and spray the tops of the sandwiches with cooking spray.
Cook on each side for 1-2 minutes or until golden brown and cheese has melted.
Cut into fourths and serve immediately, or wrap in tin foil to send to school. (Allow to cool before wrapping, otherwise the moisture from the heat will make the sandwich soggy and may also cause a food hazard.)
Cut remaining carrots into sticks and slice yellow bell pepper into rings as well. Serve sandwiches with veggies and mandarin oranges on the side.