using (var compressedFileStream = new MemoryStream())
                // using (FileStream compressedFileStream = new FileStream(@"C:\Users\antonov\Desktop\1\release.zip", FileMode.CreateNew))
                // через FileStream  файл сохраняется корректно


                //Create an archive and store the stream in memory.
                using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Create, true))
                {
                    foreach (var (filebytes, filename) in fileList)
                    {
                        //Create a zip entry for each attachment
                        var zipEntry = zipArchive.CreateEntry(filename);

                        //Get the stream of the attachment
                        using (var originalFileStream = new MemoryStream(filebytes))
                        using (var zipEntryStream = zipEntry.Open())
                        {
                            //Copy the attachment stream to the zip entry stream
                            await originalFileStream.CopyToAsync(zipEntryStream);
                        }
                    }
                    return new FileContentResult(compressedFileStream.ToArray(), "application/zip") { FileDownloadName = "Files.zip" };
                    //пробовал  менять "application/zip" на "application/octet-stream"- не помогает
                }

  using (var compressedFileStream = new MemoryStream())
                {
                    using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Create, true))
                    {                  
                        foreach (var (filebytes, filename) in fileList)
                        {
                            //Create a zip entry for each attachment
                            var zipEntry = zipArchive.CreateEntry(filename);

                            //Get the stream of the attachment
                            using (var originalFileStream = new MemoryStream(filebytes))
                            using (var zipEntryStream = zipEntry.Open())
                            {
                                //Copy the attachment stream to the zip entry stream
                                await originalFileStream.CopyToAsync(zipEntryStream);
                            }
                        }                      
                    }
                    return new FileContentResult(compressedFileStream.ToArray(), "application/zip") { FileDownloadName = "Files.zip" };
                }