Cut the chipotle or ancho peppers open; discard stems and seeds. Cut peppers into extra-small pieces. Place in a small bowl and cover with boiling water. Let stand 45 to 60 minutes to soften. Drain well.
Meanwhile, halve the chayotes or zucchini lengthwise; remove seeds. Scoop out the pulp of the chayotes or zucchini, leaving a 1/4-inch-thick shell. Chop pulp and set aside.
Cook chayote shells in boiling lightly salted water for 5 minutes. Invert the shells and drain. (Do not precook zucchini shells.)
For filling, in a large skillet cook the sweet peppers and onion in hot oil for 3 minutes. Stir in chopped chayote or zucchini pulp, drained pepper pieces, corn, tomato, and oregano. Cook, uncovered, for 5 minutes, stirring frequently. Remove from heat. Stir in bread crumbs, salt, and black pepper.
Spray a 2-quart rectangular baking dish with cooking spray. Arrange chayote or zucchini shells, cut sides up, in prepared dish. Spoon filling into shells. Bake, covered, in a 350 degree F oven for about 30 minutes or until heated through. Makes 6 side-dish servings.
Prepare and stuff the chayote. Cover and chill for up to 24 hours. Bake as directed, allowing a few extra minutes to heat through.