> Not really doable for a lot of Austria and generally the Alpine regions.
On the other hand that distance is a lot smaller than Chicago-Seattle (4x) so the lack of high speed in the alpine region isn't as noticable for a night train because the distances are much shorter.
The thing about sleeper trains is that you need the distance to be 8-15 hours. If it's less than 8h you'd get uncomfortable departure or arrival times. 10h for Zurich-Vienna is perfect for a sleeper.
On the other hand that distance is a lot smaller than Chicago-Seattle (4x) so the lack of high speed in the alpine region isn't as noticable for a night train because the distances are much shorter. The thing about sleeper trains is that you need the distance to be 8-15 hours. If it's less than 8h you'd get uncomfortable departure or arrival times. 10h for Zurich-Vienna is perfect for a sleeper.