You do not have mulitipart form data. You are not uploading anything. There is no form.
Is your epub truly bigger than 2 GB in size?
Have you tried updating to an older or newer java version on your machine since as I pointed out some recent java jdk/jre versions are broken in relation to handling zip files created by other tools.
See:
https://bugs.openjdk.org/browse/JDK-8315828
https://bugs.openjdk.org/browse/JDK-8313765