Preheat the oven to 400 degrees F (200 degrees C).

Heat oil in a deep skillet over high heat: cook each tortilla in skillet, turning frequently, until golden brown, 2 to 3 minutes per side. Drain on paper towels.

Place 4 tortillas on a baking sheet. Spread 3 tablespoons of refried beans evenly on top: add 2 to 3 tablespoons ground beef. Top with remaining 4 tortillas.

Mix taco sauce and enchilada sauce together in a small bowl: spoon 2 tablespoons on top of the tortillas evenly. Sprinkle 1/4 cup of each type of cheese evenly on top.

Bake in the preheated oven until the cheese is melted, 3 to 4 minutes. Top with diced tomatoes, black olives, and green onions. Cut into quarters: serve immediately.