For the crumb topping, stir together the granulated sugar, brown sugar, cinnamon and salt until well combined. Whisk in the melted butter. Using a wooden spoon or rubber spatula, stir in the flour just until everything is combined. Spread the mixture on a rimmed baking sheet lined with parchment paper. As the mixture dries, crumble it into coarse crumbs with your fingers. Set it aside while making the muffin batter.
Preheat the oven to 350 degrees. Grease and flour 12 jumbo muffin cups. Set the pans aside.
Shred the zucchini using the large whole side of a box grater. Place the shredded zucchini in a mesh strainer to drain while assembling the other ingredients.
For the muffin batter, in a large bowl, whisk together the eggs, sugar, oil and vanilla, and caramel extract until well blended.
Gently squeeze any excess moisture out of the shredded zucchini, then stir it into the egg mixture.
In a medium bowl. whisk together the flour, vanilla pudding mix, baking soda, baking powder and salt. Add the flour mixture to the egg/zucchini mixture and stir just until combined.
Divide half of the muffin batter between the prepared muffin cups.
Spoon a generous half of the can of Dulce de Leche into a microwave-safe bowl and heat on high for a few seconds just until the caramel warms a little-that will thin it slightly and make it easier to drop off a spoon. Give it a stir to make sure it's warmed all the way through.
Place a generous teaspoonful of the caramel in the center of the batter in each muffin cup. Gently swirl the caramel into the batter. A metal skewer used for trussing and tying a turkey or chicken to roast works great for this.
Top with the remaining muffin batter. Spoon another teaspoonful of Dulce de Leche on the center of the batter and swirl.
Sprinkle the crumb topping over each muffin.
Bake @ 350 degrees for 35-40 minutes. or until a pick inserted in the center comes out clean.
Cool in the pan for 10 minutes. Run a knife around the edge of each muffin and gently remove them from the pans to a wire rack to cool completely.