Large file download works without zipstream but fails with zipstream

I have a sample download code that works fine if the file is not zipped because I know the length and when I provide, it I think while streaming play does not have to bring the whole file in memory and it works. The below code works

     def downloadLocalBackup() = Action {
          var pathOfFile = "/opt/mydir/backups/big/backup"
          val file = new
          val path: java.nio.file.Path = file.toPath
          val source: Source[ByteString, _] = FileIO.fromPath(path)
"from local backup set the length in header as "+file.length())
          Ok.sendEntity(HttpEntity.Streamed(source, Some(file.length()), Some("application/zip"))).withHeaders("Content-
          Disposition" -> s"attachment; filename=backup")

I don’t know how the streaming in above case takes care of the difference in speed between disk reads(Which are faster than network). This never runs out of memory even for large files. But when I use the below code, which has zipOutput stream I am not sure of the reason to run out of memory. Somehow the same 3GB file when I try to use with zip stream, is not working.

    def downloadLocalBackup2() = Action {
          var pathOfFile = "/opt/mydir/backups/big/backup"
          val file = new
          val path: java.nio.file.Path = file.toPath
          val enumerator = Enumerator.outputStream { os =>
          val zipStream = new ZipOutputStream(os)
          zipStream.putNextEntry(new ZipEntry("backup2"))
          val is = new BufferedInputStream(new FileInputStream(pathOfFile))
          val buf = new Array[Byte](1024)
          var len =
          var totalLength = 0L;
          var logged = false;
          while (len >= 0) {
            zipStream.write(buf, 0 ,len)
            len =
            if(!logged) {
              logged = true;
    "logging the while loop just one time")

        }"log right before sendEntity")
        val kk = Ok.sendEntity(HttpEntity.Streamed(Source.fromPublisher(Streams.enumeratorToPublisher(enumerator)).map(x=>{val kk = Writeable.wByteArray.transform(x);kk}),
          None, Some("application/zip"))
        ).withHeaders("Content-Disposition" -> s"attachment;")