Originally Posted by
Goldorak
This has already been discussed to death in many threads... If you don't check-in in ZWE for your ZWE-AMS-KUL, then your entire itinerary will be cancelled. On the return, it is usually no problem to skip the last train leg, providing that you have exchanged your BP for the train ticket.
I can confirm you have to start from ZWE to go to AMS because they will seek confirmation that your ticket from ZWE to AMS was stamped when you are at Schiphol. Upon return you can pick up your AMS-ZWE ticket at Schiphol and it should turn up as a segment even if you do not actually take the train.