Grate zucchini on a cheese grater and add it to a large mixing bowl.
Add eggs, oil, vanilla, and brown sugar. Whisk vigorously for about a minute.
Add flour, salt, cinnamon, and baking soda. Whisk well.
Melt baking chocolate in a microwave according to the package instructions. (Remember that it's best to melt chocolate on half power and stir after every 30 seconds.)
Whisk in melted dark chocolate into the batter.
Fold in dark chocolate chips into the batter or simply add chocolate chips to the top of each muffin before baking.
Divide the batter between the muffin cups and bake for 20-22 minutes.