Exporting an object to a ZIP file
You could use try-with-resources  to efficiently close the streams, this also reduces line count and readability.

IOUtils provides a tested utility to copy between input and output streams, add commons-compress to you classpath, for example using gradle

 compile group: 'org.apache.commons', name: 'commons-compress',version: '1.14'


I simply extended the code you provided. I believe you will get the idea for reading back the zip file.

  try {

            File file = new File("C:/temp/tempExport.bef");
            file.createNewFile();

//Use try with resources to handle closing streams

            try (ZipOutputStream zipStream = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(file)))) {
                zipStream.putNextEntry(new ZipEntry("bef"));
                ObjectOutputStream objectStream = new ObjectOutputStream(zipStream);
                objectStream.writeObject(extendedFormat);
            }

         //to read the file you need a temp buffer or file to decompress the archive
            File temp = Files.createTempFile("", "").toFile();

            try (ZipInputStream zis = new ZipInputStream(new BufferedInputStream(new FileInputStream(file)));
                 BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(temp));
                 BufferedInputStream bis = new BufferedInputStream(new FileInputStream(temp))) {
                zis.getNextEntry();
                IOUtils.copy(zis, bos);
                bos.close();
                ObjectInputStream ois = new ObjectInputStream(bis);
                ExtendedFormat extendedFormat= (ExtendedFormat) ois.readObject();
            }

            temp.delete();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }