Even with smooth deceleration, the earth bulges at the equator due to centrifugal force. If you decelerate smoothly, you pass through the zero-point (no rotation) which would mean the bulge would have to disappear. This wouldn’t happen smoothly, it would happen in bursts that we call earthquakes. And then the bulge reappears once the centrifugal force is restored in the opposite spin, again in bursts.