This week's book giveaway is in the Reactive Progamming forum. We're giving away four copies of Reactive Streams in Java: Concurrency with RxJava, Reactor, and Akka Streams and have Adam Davis on-line! See this thread for details.
'&' is a special character in XML. It's used to represent "entities" such as < (for the '<' character. because that's also a special character). So it's seeing '&zs' and thinks you were intending it to be an entity like '&zs;' - entities always end in a semi-colon.
If you just want a plain ampersand character '&', you need to escape it. To do that, replace it with '&'