How to Make It
Make the coconut-cashew streusel: Stir together cashews, coconut, brown sugar, flour, and salt in a medium bowl. Add melted butter; stir to combine.
Make the muffins: Preheat oven to 350°F. Lightly coat a 12-cup muffin pan with cooking spray. Stir together flour, cardamom, salt, baking powder, and baking soda in a medium bowl; set aside.
Whisk eggs in a medium bowl until pale and foamy. Add sugar, zucchini, oil, and vanilla; whisk to combine. Gently whisk flour mixture into egg mixture until just combined. Transfer batter to prepared muffin pan, spooning about 1/4 cup batter into each cup. Top each muffin with about 2 tablespoons of the coconut-cashew streusel.
Bake in preheated oven until golden brown and a wooden pick inserted in center comes out clean, 20 to 22 minutes. Transfer pan to a wire rack; let cool 10 minutes. Run a small offset spatula around each muffin, and transfer muffins to a wire rack. Let cool completely, about 30 minutes.
Whisk together powdered sugar, coconut milk, and lime zest and juice in a small bowl until smooth. Spoon glaze over cooled muffins.