Chocolate Zucchini Bars

INGREDIENTS

• 1/2 cup butter
• 1 3/4 cups white sugar
• 1/2 cup vegetable oil
• 2 eggs
• 1 teaspoon vanilla extract
• 2 1/2 cups all-purpose flour
• 1/2 teaspoon salt
• 4 tablespoons unsweetened cocoa powder
• 1 teaspoon baking soda
• 1/2 cup sour milk
• 1 1/2 cups grated zucchini