hadoop-zookeeper-server service refers to itself as ZooKeeper in user visible messages

On RPM based systems the service is called hadoop-zookeeper. On DEBs it is called hadoop-zookeeper-server
and worse yet indetifies itself as /etc/init.d/ZooKeeper :

service hadoop-zookeeper-server
Usage: /etc/init.d/ZooKeeper

{start|stop|restart|force-reload|status|force-stop}