Read from multiple files and merge them in a stream by condition

Question
1

I have several csv files with next structure
{“unixTimestampMs”:1609531200000,“timezoneId”:“Europe/Moscow”,“payload”:…}

I need to read all of them in a zstream by time condition. (ex. take 10 records from first file, then 5 records from second file, 15 records from third file and so on by round robin system and ordered by time)

Previously I had single file and it was like that:

def fileStream: Stream[Throwable, Result] =
    for {
      res <-
        fileSource(appConf.sourceFilePath)
          .mapZIO(transactionService.mkMsgFromString)
          .collectSome
          .groupAdjacentBy(_.unixTimestampMs)
          .map(evenlyDistributeMessages)
          .flatMap(ZStream.fromChunk(_))
          .mapZIO(sleepIfRequired)
          .mapZIOPar(proxyConf.maxConnections, proxyConf.maxConnections)(emitMessage(_, uriToSendMessages))
    } yield res

where

def fileSource(file: String): Stream[Throwable, String] =
    ZStream
      .acquireReleaseWith(transactionsFileService.getFileAsSource(file))(releaseFile)
      .flatMap(f => ZStream.fromIterator(f.getLines().drop(1), 256))

so fileSource gives me my expected stream.
How to rewrite it for multiple files case and merge in a zstream ordered by time?