Preheat the oven to and 400 °F lightly spray an 8x8-inch casserole dish with nonstick spray.
Heat the oil in a large skillet over medium heat. Cook the summer squash, onion and garlic until the onion turns soft and translucent and the squash is soft.
Add the soy crumbles, cumin, paprika, salt, pepper and chopped tomatoes. Bring the mixture to a simmer, put the lid on, and simmer for a few minutes until the tomatoes have softened.
Arrange the taco shells in the baking dish. Spoon the taco filling into each taco shell and evenly sprinkle the cheese on top.
Bake for about 15 minutes, until the cheese is melted and the taco shells have lightly browned.
Top salsa and a dollop of Greek yogurt.