It is advisable to start a new question as your topic is not related to this one.
Holding the Swiss Half Card, you can’t buy the tickets in advance, but you can at the base station in Zermatt, by showing the Swiss Half Fare Card. You can present it as an e-ticket.
It is not recommended to buy mountain excursion tickets in advance. The weather plays a major part in the mountains, it would mean a waste of money in case of bad weather.