- Preheat the oven to 325°F. Lightly grease a 9" x 13" pan.
- In a large mixing bowl, beat together the butter, oil, sugar, vanilla, baking soda, baking powder, and salt until smooth.
- The flaxseed meal packaging generally has the ratio for substitutions. I believe it's 1 tbsp flaxmeal in 3 tbsp water for 1 egg. In this case since there were 2 eggs, I took twice that amount. Keep it for a few minutes. Then add it to the batter/
- Stir in the yogurt alternately with the flour.
- Add the cocoa and espresso powder, mixing until smooth.
- Fold in the zucchini and 1/2 cup chocolate chips. Spoon the batter into the prepared pan.
- Bake the cake for 30 to 35 minutes, until the top springs back lightly when touched, and it seems set.