Chocolate Zucchini Cake

I tried a new recipe for Chocolate Zucchini Cake. It is a bundt cake which appealed to me because just one pan to wash. I followed all the directions on mixing it, put it in the oven, and OHHHH! it smelled so good. Times up! Took it out of the oven, Looking Good, put it on the rack to cool and before my very own eyes saw it flattened down like a pan cake. Took the cake out of the pan and it was quite heavy. Put the glaze on it which made it heavier. What Happened????? I checked the recipe again and yes I followed all the directions and used all the right ingredients but discovered that my baking powder expired in 2007. Grandpa went down town today and purchased new baking powder and said "try again". Ÿ