Preheat the oven to 350 degrees F (175 degrees C).
In a large bowl, beat eggs with sugar for about 10 minutes or until thickened and pale. Blend oil and cooled chocolate into the beaten egg mixture.
In a small bowl stir together flour, baking powder, baking soda and salt; stir flour mixture into egg mixture until just blended. Stir in zucchini and chopped nuts. Using an ice-cream scoop, spoon batter into 24 paper-lined or greased muffin cups, filling the cups 2/3 full.
Bake for 20 minutes or until fork or toothpick inserted in a cupcake's center comes out clean. Let cool in pans on rack for 10 minutes. Remove from pans; let cool completely. Spread with chocolate frosting and garnish with walnut or pecan halves.