Preheat the oven to 375°F (190°C). Grease the muffin tin or line it with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt until well combined.
In a separate bowl, mix the milk, vegetable oil, eggs, vanilla extract, and orange zest (if using) until fully combined.
Pour the wet ingredients into the dry ingredient mixture and stir gently with a rubber spatula until just combined. Be careful not to overmix.
Fold in the cranberries gently, ensuring they are evenly distributed within the batter.
Spoon the batter evenly into each muffin cup, filling them about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Once baked, remove the muffins from the oven and let them cool in the tin for about 5 minutes. Then transfer them to a cooling rack to cool completely.