In a large pan, cook bacon just until fat begins to render and bacon softens.
Add the onion and garlic and cook until onion is tender.
Place some zucchini in a single layer across the bottom of pan.
Top with some tomatoes.
Repeat layering until all vegetables are in the pan.
Simmer, covered, on medium-low heat, for 5-10 minutes, then turn vegetables with spatula to brown and cook the other side.
Top vegetables with marinara sauce and cheeses, and continue to cook, covered, for 5-10 minutes more or until vegetables are tender and cheese is melted.