There is only one class that is realizing the zooming functionality: ZoomManager.
Check out the examples on how to use the ZoomManager: Examples.
This project is synced to Maven Central, so you can just add the following dependency to your project:
<dependency>
<groupId>com.github.kerner1000</groupId>
<artifactId>javafx-chart-zooming</artifactId>
<version>0.0.8</version>
</dependency>