protected void ZipDownload()
{
  var zip = new ZipFile(@"C:\Users\(myuser)\Desktop\desktop.zip");

  Response.Clear();
  Response.AddHeader("content-disposition", "attachment;filename=docs.zip ");
  Response.ContentType = "application/zip";

  using (var memoryStream = new MemoryStream())
  {
    zip.Save(memoryStream);
    Response.BinaryWrite(memoryStream.ToArray());
  }

  Response.End();
}