From Ambari Web, browse to Services > ZooKeeper.

Start ZooKeeper by selecting Service Actions > Start. This will push the new ZooKeeper configurations and start the ZooKeeper servers.

Save the old ZooKeeper configuration and add symlink from /etc/zookeeper/conf:

mv /etc/zookeeper/conf /etc/zookeeper/conf.saved

ln -s /usr/hdp/current/zookeeper-client/conf /etc/zookeeper/conf

ls -la /etc/zookeeper

total 4
drwxr-xr-x 3 root root 4096 Jun 19 21:51 2.3.0.0-2323
lrwxrwxrwx 1 root root   35 Jun 19 21:54 conf -> /usr/hdp/current/zookeeper-client/conf
drwxr-xr-x 2 root root 4096 Jun 14 00:11 conf.saved