Preheat the oven to 375°F and lightly grease a loaf pan. In a large bowl, combine the ground beef, ground pork, breadcrumbs, egg, onion, 2 cloves of minced garlic, oregano, half the feta, 1 teaspoon salt, and black pepper. Mix gently until just combined, then press the mixture into the prepared pan.
Bake the meatloaf for 50 to 55 minutes until it reaches an internal temperature of 160°F. While it bakes, stir together the Greek yogurt, grated cucumber, remaining clove of minced garlic, dill, and remaining 0.5 teaspoon salt to make the tzatziki. Set it aside in the refrigerator.
Cook the orzo in boiling water according to package directions, then drain and rinse under cold water. Toss the orzo with olive oil, lemon juice, lemon zest, cherry tomatoes, parsley, and the remaining feta. Let the meatloaf rest for 10 minutes before slicing. Serve slices with a spoonful of tzatziki and a portion of the orzo salad on the side.