Preheat the oven to 177°C (350°F) and line a 12-pan muffin tray.
In a large bowl, combine the flour, baking powder, baking soda, salt, nutmeg and cinnamon. In a separate bowl, stir together the milk, oil, vanilla, brown sugar and granulated sugar.
After grating the zucchini, give it a wee squeeze if it's quite wet before stirring it into the wet ingredients.
Add the wet ingredients to the dry and stir until almost combined - a few patches of flour here and there are OK - and add the chocolate chips. Stir the batter together until all the flour is just combined. Don't over-mix.
Fill each lined muffin mould ¾ of the way up with the batter. You are ready to bake now or you can add the oat topping.
For the oat topping, combine the oats, sugar and cinnamon in a small bowl and spinkle on top of each muffin. Pop the tray in the oven and bake for 25-minutes or until the muffins have risen in to a dome and a skewer comes away from the centre clean.
Remove from the oven and allow them to sit for 10-minutes before turning them out. Serve warm or at room temperature.