Create zip archive from a list of ByteArrayInputStream and return byte[] array of the archive - JAVA

I want to archive some files that I am receiving from an external source. I receive each of this files as a ByteArrayInputStream. In the end I want my method to create the zip archive and return a byte[] array so that I can download it later. I have successfully managed to do this, but the end result is an ZipOutputStream and not the byte[] array that I need. Any ideeas are appreciated. Thanks!

       FileOutputStream fos = null;
       ZipOutputStream zipOut = null;

       try {
           fos = new FileOutputStream(archiveFileName.concat(ReportFormat.ZIP.getFileExtension()));
           zipOut = new ZipOutputStream(new BufferedOutputStream(fos));

           for (Map.Entry<?, ByteArrayInputStream> entry : mapInputStream.entrySet()) {
               String  fileFromInsiteArchiveName = (String) entry.getKey();
               ByteArrayInputStream inputStream = entry.getValue();

               ZipEntry zipEntry = new ZipEntry(fileFromInsiteArchiveName);
               zipOut.putNextEntry(zipEntry);
               byte[] tmp = new byte[4 * 1024];
               int size = 0;
               while ((size = inputStream.read(tmp)) != -1) {
                   zipOut.write(tmp, 0, size);
               }
               zipOut.flush();
               inputStream.close();
           }
           zipOut.close();

           return zipOut;

       } catch (FileNotFoundException e) {
           //handle this
       } catch (IOException e) {
           //handle this
       } finally {
           try {
               if (fos != null) fos.close();
           } catch (Exception ex) {
               //handlethis
           }
       }
       return zipOut;
   }

Copy to ByteArrayOutputStream and then do baos.toByteArray() to get your byte[]