Preheat oven to 350 degrees. Line a loaf pan with parchment paper.
Make the chocolate batter:
Whisk together the flour, sugar, cocoa powder, baking soda, and salt. Add the oil, vanilla, vinegar, water, and chocolate chips and mix together. Set aside.
Make the pumpkin batter:
Whisk together the flour, sugars, baking powder, baking soda, nutmeg, cinnamon, and salt. Add the oil, vanilla, pumpkin, and water, and mix together. Set aside.
Put it together:
Spoon the batter into the pan, alternating between the pumpkin and chocolate to make a marbled pattern. For example, do chocolate, pumpkin, chocolate pumpkin, and then do another layer on top - pumpkin, chocolate, etc.
Bake at 350 degrees for about 40-50 minutes. Remove from oven and allow to cool in pan for about 30 minutes, then remove by using the parchment paper to lift the cake out.