Preheat your oven to 350°F. While it heats, prepare a loaf pan (approximately 8x4 inches or 9x5 inches) by greasing it well with butter or cooking spray, then lining the bottom with parchment paper for easy removal. This ensures your bread won't stick and gives you clean edges.

In a medium bowl, whisk together the almond flour, coconut flour, vanilla protein powder, monkfruit powder, salt, baking powder, and xanthan gum. Make sure everything is evenly combined with no lumps, especially the xanthan gum, which can clump easily. Set this dry mixture aside—the xanthan gum will help give your bread structure since this keto version lacks traditional gluten.

Separate your room-temperature eggs carefully, making sure no yolk gets into the whites. In a clean, dry bowl, beat the egg whites using an electric mixer on high speed until stiff peaks form—this takes about 3-5 minutes. Stiff peaks are essential here because they'll create lift in your bread, compensating for the lack of traditional flour structure. Set the whites aside in a separate clean bowl.

In a large bowl, combine the egg yolks, melted and cooled butter, lemon juice, lemon zest, and vanilla extract. Whisk until well combined and smooth. Add the dry ingredient mixture from Step 2 to this wet mixture and stir until just combined—don't overmix. Now fold in the squeezed zucchini (it's crucial that it's very dry to prevent a soggy loaf, so squeeze it well). I like to add the zucchini last so it distributes evenly throughout the batter without deflating it.

Gently fold the stiff egg whites from Step 3 into the batter using a spatula, working in two additions if needed. Fold slowly and deliberately to maintain the airiness—this is what gives your bread its tender crumb. Once the whites are mostly incorporated with just a few streaks remaining, fold in the white chocolate chips. Pour the batter into your prepared pan from Step 1, smoothing the top gently.

Place the pan in your preheated 350°F oven and bake for 45-50 minutes, until a toothpick inserted in the center comes out with just a few moist crumbs (not wet batter). The top should be golden brown. Since keto baked goods can brown quickly due to their ingredients, check at the 40-minute mark—if the top is browning too fast, tent it loosely with foil for the remaining time.

Remove the pan from the oven and let the bread cool in the pan for at least 30-45 minutes. This cooling time is important because the crumb continues to set during this period. I've found that rushing this step results in the bread crumbling when you try to remove it. Once cooled, run a thin knife around the edges and turn the bread out onto a wire rack to cool completely before slicing.