But even that would only save a few minutes. If all goes perfectly it can be done, but any delay or long queue in immigration and this plan is out the window.

This would most likely not solve the issue for the OP. As a side remark: Traveling from Ostbahnhof to Hauptbahnhof by rail and not using the S-Bahn tunnel takes quite a while....

That won't impact customs at all.

What will impact customs is whether the OP has to declare anything or not and whether he gets stopped for an inspection if not declaring anything.

sometimes it helps to quote everything I wrote, rather than extracting one sentence in the attempt to make one look stupid. :(

good thing is that everybody else understood what I wrote.

besides, a lot of people mean the whole process of exiting an airport from arrival when talking about "customs" ..

The airport to Ostbahnhof trip is shorter and platform changes take less time than at Hauptbahnhof. Add to that the time that it takes Railjet to get to M-Ost.

It would save him roughly 20 minutes in making his connection. Never understood why that train doesn't make the stop. Moot anyway, since it doesn't.

In any case, the customs issue was dealt with weeks ago! ;)

His issue was being able to catch a Railjet train 90 minutes after touchdown. He assumed that customs (and possibly Syrians) would be the main obstacle. Which isn't the case. :D

I know I know...we're going around in circles! ;)