You can make a valid APK/IPA/JAR polyglot, just put all the files in one folder, and use the jar tool to make it back into a zip, then rerun jarsigner because t

You can make a valid APK/IPA/JAR polyglot, just put all the files in one folder, and use the jar tool to make it back into a zip, then rerun jarsigner because the APK has to be resigned after adding the Java and iOS files.