You've declared your classpath entry incorrectly, and have put a fileset element pointing to your java classes (probably your POJO classes). It's basically trying to unzip your class files. To fix it you need to specify the location of your classes using pathelement instead, with the location pointing to the base directory of your package. For example:
Code:
<path id="hibernate-schema-classpath">
<fileset dir="${basedir}/libraries">
<include name="**/*.jar"/>
<include name="**/*.zip"/>
</fileset>
<pathelement location="${hibernate-pojo-classes}" />
</path>