Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius) and line a 12-cup muffin tin with parchment liners.

Grate fresh zucchini and wrap in a clean towel, squeezing firmly to remove all excess liquid until only 1.5 cups of dry pulp remains.

In a large mixing bowl, beat eggs, peanut butter, erythritol, and vanilla extract until a uniform emulsion forms.

Stir in the squeezed zucchini, baking soda, salt, and cinnamon until thoroughly incorporated.

Fold in sugar-free chocolate chips if using.

Divide the batter equally among the muffin liners.

Bake for 22 to 25 minutes or until the center is set and the edges are lightly browned.

Remove from oven and let cool completely in the pan to allow the flourless structure to stabilize.