Sonian isn't using the ZooKeeper Plugin anymore, but you might want to look at some of the community forks that are more actively maintained:
- https://github.com/grmblfrz/elasticsearch-zookeeper
- https://github.com/imotov/elasticsearch-zookeeper
Alternatively, you should very seriously consider using a dedicated masters setup, as mentioned by imotov in this thread.