The existing answers already explain why yeast and baking powder won't work together. But even if they did, you wouldn't have a reason to use them. You seem to think that fluffiness depends on the amount of gas produced by the leaveners. In fact, it depends on both the gas and the ability of the dough to trap that gas.
Besides, can yeast be used in place of baking powder?
Generally this is done by adding equal parts baking soda and lemon juice to equal the amount of yeast called for in the recipe. You can also use buttermilk in place of lemon juice or a mixture of milk and vinegar. Alternatively you can use baking powder, which is a combination of baking soda and an acid.
What is the difference between yeast and baking powder?
Difference Between Baking Powder & Yeast. Baking powder gets its power from a chemical reaction that produces air bubbles, whereas yeast is an actual living organism, producing gas from a biological reaction. The two processes are not similar at all, and the two products are not interchangeable in recipes.