Add files to existing zip inside a blob storage [Stream is not seekable] #700

private static async Task Compress(string sourceFileName, string sourceFileUrl)
{
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(Environment.GetEnvironmentVariable("AzureWebJobsStorage"));
    CloudBlobClient outputClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer outputContainer = outputClient.GetContainerReference("zip-container");
    CloudAppendBlob outputBlob = outputContainer.GetAppendBlobReference("Test.zip");

    using var httpClient = new HttpClient();
    Stream sourceStream = await httpClient.GetStreamAsync(sourceFileUrl);

    if (!await outputBlob.ExistsAsync())
    {
        await outputBlob.CreateOrReplaceAsync();

        using var zipStream = new ZipOutputStream(await outputBlob.OpenWriteAsync(false));

        zipStream.SetLevel(3);

        ZipEntry zipEntry = new(sourceFileName);
        zipEntry.DateTime = DateTime.Now;

        zipStream.PutNextEntry(zipEntry);

        StreamUtils.Copy(sourceStream, zipStream, new byte[4096]);

        zipStream.CloseEntry();
    }
    else
    {
        ZipFile zipFile = new(await outputBlob.OpenWriteAsync(false)); //Exception: Stream is not seekable

        zipFile.BeginUpdate();

        CustomStaticDataSource sds = new();
        sds.SetStream(sourceStream);

        zipFile.Add(sds, sourceFileName);

        zipFile.CommitUpdate();

        zipFile.Close();
    }
}