Hi Andre,
Do you have a batch or streaming use case?
Flink provides Cassandra Input and OutputFormats for DataSet (batch) jobs and a Cassandra Sink for DataStream applications. The is no Cassandra source for DataStream applications.
Regarding your error, this looks more like a Zepplin configuration issue to me.
It seems that the JAR file is not correctly added to the classpath.
Best,
Fabian