Preheat oven to 350F and prepare 2 baking sheets with parchment paper.
In a large bowl, whisk together the eggs, sugar, vegetable oil and zest.
Add the flour and baking powder and stir with a wooden spoon. The mixture will resemble a very soft bread dough. Stir in the almonds (or other ingredient combinations as suggested) and distribute evenly throughout the dough.
Divide the dough into three pieces. On a lightly floured surface, shape each piece into a log approximately 30 cm long by 8 cm wide. Transfer each log onto the baking sheet.
If you are trying all 3 variations, divide the dough into 3. Kneed 2/3 cup of ingredients (2/3 cup of almonds; 1/3 cup each pistachios and almonds; 1/3 cup each hazelnuts and chocolate chips) into each dough.
Bake in the centre of the oven for approximately 40 minutes or until lightly golden in color.
Transfer to a wire rack and let cool for 15 minutes.
Reduce the oven temperature to 275F. Place each log on a cutting board. With a serrated knife, slice each log into 1 cm cookies. Transfer the cookies back onto the baking sheets and continue baking for about 20 minutes, flipping halfway, or until the desired level of crispness.
Transfer to the wire rack and let cool completely.