Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a mixing bowl, whisk together the melted butter and sugar until combined.

Add the eggs, vanilla extract, lemon zest, and lemon juice. Mix until smooth.

In another bowl, combine the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the grated zucchini.

Pour the batter into the prepared baking pan and spread evenly.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Remove from the oven and let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

In a small bowl, whisk together the powdered sugar and lemon juice until smooth.

Once the bars are completely cooled, drizzle the glaze over the top.

Cut into squares and serve.