JavaLangAccess has a method (newStringUTF8NoRepl) to create a String from UTF8 that is solely used by ZipCoder. The buffer from ZipCoder should not be shared and added an additional argument to String.newStringUTF8NoRepl.
If ZipCoder copies the byte array it can call JLA.uncheckedNewStringNoRepl(byte[] bytes, Charset cs)
and the String code can be simplified.