Preheat oven to 325 degrees F.
Cut zucchini into 1/8-inch slices.
Heat shortening in a large skillet.
Add onions and cook over medium heat until transparent.
Add zucchini and cook until just tender, turning occasionally.
Add tomatoes, parsley, salt, pepper, oregano, 1/2 C. bread crumbs, and cheeses.
Stir in eggs.
Grease 11-inch pie pan or a 14-inch pizza pan and coat well with 1 T. bread crumbs.
Pour zucchini mixture into prepared pan and spread out evenly.
Sprinkle with remaining breadcrumbs (1 T.) and bake for 1 hour and 15 minutes.
Let cool slightly.
Cut into wedges and serve.