Preheat oven to 400 degrees F (200 degrees C). Lightly grease a 9x5-inch loaf pan with oil.
Place bread and milk in a small bowl. Press bread with a fork to soak up the milk.
Combine lamb, egg, garlic, thyme, Worcestershire sauce, lemon zest, coriander, basil, rosemary, salt, and pepper in a medium bowl. Add soaked bread; discard the leftover milk. Mix with hands until well combined. Transfer meatloaf to the prepared pan.
Combine tomato sauce and mint; spread evenly over the meatloaf. Drizzle with balsamic vinegar.
Bake in the preheated oven until no longer pink in the center, about 35 minutes. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C). Remove and let cool for 5 minutes before serving.