Hello,
If you look at the convert method : http://doc.xceedsoft.com/products/Zip/sources/convert_method.htm, you can use the Convert Preprocessing event that will allow you to give a different name for the destination file. Granted, the performance won't be mind blowing (since it will actually rebuild a zip file)but it's a start.
At the time being, this is the only option available, Xceed Zip for .NET would however, allow you to do this quite easily :).
Mathieu Drimonakos
-Technical Designer-