Preheat the oven to 425 degrees . In a bowl, soak the bread in the milk to soften.
Place a rack on a large baking sheet. Drizzle the EVOO into a large bowl. Add the lamb and beef and season with salt and pepper. Squeeze out the excess liquid from the bread and crumble it into the meat. Mix in the cheese, parsley, mint, oregano, garlic, egg and lemon zest. Roll the meat into 1 1/2- to 2-inch balls. Arrange on the prepared baking sheet and roast until browned, 12 to 15 minutes. Douse with the lemon juice.
Using a food processor, pulse the first 5 dipping sauce ingredients; season with salt and pepper. Serve with the meatballs.
For the spinach: In a large skillet, cook the garlic in the EVOO over medium-high heat. Add the spinach to wilt; season with salt, pepper and nutmeg. Sprinkle the lemon juice on top. Serve with the pita.