1. Preheat the oven to 350 degrees F. Grease a 10-inch Bundt or fluted tube pan and set aside.

For the topping:

1. Melt the butter in a small saucepan over medium heat. Stir in the brown sugar until it dissolves and begins to bubble. Stir in the chopped walnuts. Spoon the mixture into the bottom of the prepared pan.

For the cake:

1. Sift together flour, salt, baking soda, cinnamon, nutmeg, and allspice into a medium bowl. Whisk to combine thoroughly. Set aside.
2. In a large bowl using a hand or stand mixer; cream butter and shortening until thoroughly combined. Add the white and brown sugars and beat until creamy and smooth. Add eggs one at a time beating well after each addition. Add the half-and-half and vanilla and beat until combined. Add the flour and beat on low until just combined. (Do not over-mix). Stir in the zucchini and walnuts. Pour the batter evenly over the topping in the prepared pan.
3. Bake 50 to 60 minutes or until lightly brown and a toothpick or cake tester inserted into the center of the cake comes out clean. Cool the cake in the pan for 10 minutes on a wire rack. Invert cake onto a serving plate and cool completely. Slice, serve, and enjoy!