Heat 1 tablespoon oil in a deep skillet over high heat. Pan-fry each tortilla turning frequently, adding more oil as needed, until golden brown, 2 to 3 minutes per side. Allow to drain on paper towels.
Preheat the oven to 400 degrees F (200 degrees C).
To assemble each pizza, place 4 fried tortillas on a baking sheet. Spread 3 tablespoons of refried beans evenly on top of every other tortilla, then add 2 to 3 tablespoons ground beef. Place the other 4 tortillas on top.
Mix together the taco sauce and enchilada sauce in a small bowl. Spoon 2 tablespoons of the mixture on top of the tortillas and spread evenly. Sprinkle ¼ cup of each type of cheese evenly on top.
Bake in the preheated oven until the cheese is melted, 3 to 4 minutes. Remove from the oven and top with diced tomatoes, black olives, green onions, and any additional garnishes. Cut into quarters, and serve immediately.