Preheat oven to 425℉. Lightly grease a 10 inch cast iron skillet (or similarly sized oven-safe baking dish) and set aside.

In a large bowl, add dry ingredients: flour, baking powder, baking soda, salt, and garlic powder. Whisk to remove clumps.

Grate cold butter using the large side of a box grater and add to flour mixture along with buttermilk, grated zucchini (squeeze liquid out before adding to dough), chives, and shredded cheese. Gently stir until a shaggy, sticky dough forms. Turn dough out onto a floured surface.

Gently pat dough with lightly floured hands into a large, flat rectangle, about 10-12 inches wide and about ¾ inch thick. Fold dough rectangle in half, turn clockwise, and gently pat back into a large rectangle. Repeat 4 times, folding your dough 5 times in total. Pat dough into a large rectangle, about ¾ inch thick.

Using a 2.5 to 3 inch biscuit cutter, cut biscuits out of dough (do not twist your cutter, this will seal the edges). Reform leftover dough gently and continue cutting until all dough is used - you should get about 8 large biscuits. If you don't have a biscuit cutter, slice dough with a knife into squares.

Arrange biscuits in prepared skillet (they should be barely touching) and bake for about 18-20 minutes, or until lightly browned across the tops and fluffy. Remove from oven and serve warm.