Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a mixing bowl, whisk together the flour, sugar, baking powder, and salt.
In another bowl, beat the eggs, vanilla extract, and orange zest until combined.
Gradually add the wet ingredients to the dry ingredients, mixing until a dough forms. Stir in the chopped almonds.
Divide the dough in half and shape each half into a log about 12 inches long and 2 inches wide. Place the logs on the prepared baking sheet.
Bake for 25-30 minutes, or until the logs are golden brown. Remove from the oven and let cool for 10 minutes.
Reduce the oven temperature to 325°F (165°C). Using a serrated knife, cut the logs into ½-inch thick slices. Place the slices cut side down on the baking sheet.
Bake for an additional 10-15 minutes, or until the biscotti are crisp and golden. Let cool completely before serving.