Preheat your oven to 375°F (190°C) and line a muffin tin with liners.

In a large bowl, whisk together the granulated sugar and eggs until the mixture is pale and thick.

Add the lemon zest, vanilla extract, and oil to the egg mixture, and whisk until combined.

Stir in the shredded zucchini and thyme.

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

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

For the topping, mix brown sugar, flour, and butter until crumbly.

Use an ice cream scoop to fill the muffin liners with the batter.

Sprinkle the topping mixture over each muffin.

Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean.

Let the muffins cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.