Use the nicest, most intact phyllo sheets for the bottom and top layers; use sheets with tears or ones that are smaller than the size of the pan in the middle layers, where their imperfections will go unnoticed.
1. FOR THE SUGAR SYRUP: Bring all ingredients to boil in small saucepan over medium-high heat and cook, stirring occasionally, until sugar has dissolved, about 5 minutes. Transfer syrup to 2-cup liquid measuring cup and let cool completely. Discard spices and zest; set aside.
2. FOR THE NUT FILLING: Pulse almonds in food processor until very finely chopped, about 20 pulses; transfer to bowl. Pulse walnuts in food processor until very finely chopped, about 15 pulses; transfer to bowl with almonds and toss to combine. Measure out 1 tablespoon nuts and set aside for garnish. Add sugar, cinnamon, cloves, and salt to nut mixture and toss well to combine.
3. FOR THE PASTRY:
Adjust oven rack to lower-middle position and heat oven to 300 degrees. Lay 1 phyllo sheet in bottom of greased 13 by 9-inch baking pan and brush thoroughly with oil. Repeat with 7 more phyllo sheets, brushing each with oil (you should have total of 8 layers of phyllo).
4. Sprinkle 1 cup nut filling evenly over phyllo. Cover nut filling with 6 more phyllo sheets, brushing each with oil, then sprinkle with 1 cup nut filling. Repeat with 6 phyllo sheets, oil, and remaining 1 cup nut filling.
5. Cover nut filling with 8 more phyllo sheets, brushing each layer, except final layer, with oil. Working from center outward, use palms of your hands to compress layers and press out any air pockets. Spoon remaining oil (about 2 tablespoons) on top layer and brush to cover surface.
6. Using serrated knife with pointed tip, cut baklava into diamonds. Bake until golden and crisp, about 1½ hours, rotating pan halfway through baking. Immediately pour all but 2 tablespoons cooled syrup over cut lines (syrup will sizzle when it hits hot pan). Drizzle remaining 2 tablespoons syrup over surface. Garnish center of each piece with pinch reserved ground nuts. Let baklava cool completely in pan, about 3 hours, then cover with aluminum foil and let sit at room temperature for 8 hours before serving.