The chocolate flavor in this bread is nice and light (there’s only 2 Tablespoons cocoa powder for the entire loaf). If you want to go for a deeper chocolate flavor, you can add another Tablespoon of cocoa powder to the batter and stir in some mini chocolate chips (about 1/4 cup).
When we used to bake this at mom’s we would put 1/4 cup chocolate chips on top of the batter before baking to add a chocolate chip layer on top. Sometimes they would fall off and get messy, but it added a sweet chocolate layer to the bread. You can give that a try if you want a more decadent Chocolate Zucchini Bread.