Preheat your oven to 350°F and line two baking sheets with parchment paper.
In a medium bowl, whisk together almond flour, oat flour, baking powder, baking soda, and salt.
In a large bowl, cream the softened coconut oil, sugar-free sweetener, and lemon zest until light and fluffy.
Beat in the eggs and vanilla until smooth.
Alternately add the dry ingredients and Greek yogurt, mixing just until everything is combined.
Scoop about 2 tablespoons of dough per cookie onto the prepared baking sheets, leaving a couple inches between each. Flatten each mound into a round cookie about 3 inches wide and ½ inch thick.
Bake for 10–12 minutes, rotating the tray halfway through, until the cookies are lightly golden and set.
Let cookies cool on the pan for a few minutes, then transfer to a wire rack to cool completely before glazing.
To make the glaze:
In a bowl, mix the powdered sugar-free sweetener, 2–3 tablespoons almond milk, sugar-free syrup, and vanilla until smooth and spreadable.
Spread the vanilla glaze over one half of each cooled cookie and let it set.
Stir the cocoa powder into the remaining glaze, adding 1–2 more tablespoons of almond milk as needed.
Frost the other half of each cookie with the chocolate glaze. Let them fully set before serving or storing.