Apache ZooKeeper is a crucial part of Streams 4.0. Making sure you have good ZooKeeper performance is the first step to good Streams performance from an administrative perspective. ZooKeeper performance will not cause your applications to perform better or worse in most situations, but will greatly affect administration.
Here are some useful links to help you configure ZooKeeper for Streams.
IBM InfoSphere Streams Knowledge Center Links:
Section 3 of Migration to Streams 4.0 for Administrators