Make the cake: Preheat oven to 325º F. Grease a bundt cake pan liberally then dust with cocoa powder.
In a stand mixer with paddle attachment, whip together the softened butter, oil, and sugar for a couple of minutes. This helps emulsify it and results in a better overall texture.
Mix in the eggs, vanilla, and sour cream, then add the dry ingredients and mix until JUST combined in a smooth batter.
Add in the zucchini and chocolate chips and just give it a few pulses to incorporate evenly in the batter.
Spoon the batter into the pan and bake for 45-55 minutes (sometimes mine takes quite a bit longer if I use a lot more zucchini), until a toothpick inserted comes out clean.
Let cool in pan for about 15 minutes. Then flip onto a cooling rack or plate.
Make the ganache: Put the chocolate chips and whipping cream in a microwave-safe bowl (you can also do this in a double boiler on the stove). Microwave for 45 seconds to start, stir or whisk.
Repeat for 30-second increments, stirring between each. You don't want to boil or scald the cream or burn the chocolate, and whisk vigorously because there's a magic moment when the chocolate will just give and you'll have a magical creamy ganache (usually takes 3 or 4 "30 second" increments).
Spoon or pour the ganache over your cake, helping it drip down the sides. Cover most of the cake to help keep it moist. Let set.