Pre-heat oven to 375 degrees F.
Arrange pita chips on an oven-safe baking dish or baking sheet
In a skillet over medium heat, add ground meat, oregano, salt, 1 teaspoon garlic and pepper, stirring to break up large pieces until browned, about 5 minutes. Drain meat well.
Top pita chips with ground meat, mozzarella cheese and feta and bake in center of oven until cheeses are melted, but not brown, about 5 minutes.
Remove from oven and top with diced cucumbers, tomatoes, onions and olives.
In the same pan you cooked the beef, heat 1 Tablespoon olive oil and remaining 1 Tablespoon minced garlic, stirring just to heat the garlic, do not brown. Remove pan from heat, drizzle garlic olive oil over nachos. Drizzle tzatziki sauce, and sprinkle with chopped oregano.