Preheat your oven to 350°F (175°C) and line a loaf pan with parchment paper.
In a large mixing bowl, combine almond flour, whey protein isolate, ground flaxseed, coconut flour, baking powder, and salt. Mix well to ensure all dry ingredients are evenly distributed.
In another bowl, whisk together the eggs, almond milk, olive oil, and apple cider vinegar until well combined. Gradually add the wet ingredients to the dry mixture, stirring until a thick batter forms.
Transfer the batter to the prepared loaf pan and smooth the top with a spatula. Bake in the preheated oven for 40-45 minutes or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Slice and serve as desired.