Finely grate zucchini and wrap in clean kitchen towel
Squeeze out as much moisture as possible — repeat twice
Whisk melted butter sugar eggs and vanilla until combined
Add cocoa powder flour baking soda and salt
Fold gently until just combined — do not overmix
Fold in squeezed dry zucchini until evenly distributed
Fold in chocolate chips if using
Preheat air fryer to 325°F (163°C) for 3 minutes
Spray a 7 inch pan with cooking spray
Pour batter into prepared pan and smooth top
Place in air fryer basket
Cook for 14-16 minutes until top is set and crackly
Toothpick should come out with moist crumbs not wet batter
Cool completely in pan before cutting into squares
Cut into 9 equal squares and serve
