Yes, I did test their system. Every time I tried, though, clicking on "Purchase Tickets" led to the error "Service is currently unavailable!". I tried several times over the course of 5 days.
The basic question is whether whether ZS is actually connected to the EPA or not.
Any ideas? I'm thinking either one of the station numbers is wrong, or the train is under some other number.
Sometimes with trains in EPA you need to add a 0 or 00 in front of a train number. No guarantees that it will help, but if you have access to the terminal, why not to try?