ForceUser said:If you mean cleaving between multiple heads, the answer is no. The sidebar in the 3.5 MM states that the hydra is designed to reward characters with the Improved Sunder feat and player groups with good teamwork. Allowing a person to cleave or great cleave or whirlwind multiple heads as though they belonged to multiple creatures would work counter to that stated purpose. At the end of the day, the hydra is a single creature regardless of its heads' special properties.
What does Improved Sunder have to do with fighting a hydra?