Preheat oven to 180 C temp. Line a muffin pan with paper liners.

In a big bowl, whisk the eggs and sugar. Add the buttermilk, oil, vanilla extract. Whisk until well combined.

In another bowl, whisk the flour, cacao, baking powder, and salt together. Add this mixture to the wet ingredients bowl and stir just until combined.

Add the grated and drained zucchini, stir just until combined.

Divide the batter between 12 muffin pan. Top with blueberries and lightly press them into the batter.

Bake for 25-30 min.