Hello KanwerPradeep
You can buy a ticket from Zürich HB to Münich Hbf. While purchasing the ticket, there is a reduction type field “Discount cards”, select “GA travel card”. The ticket will then be issued taking into account your Swiss Travel Pass to the border; you will receive a ticket respectively at zero cost and only charge the German stretch. However, it will include the seat reservation from Zürich HB.
Once more: You really have to check if it makes sense to activate a Swiss Travel Pass Day for that journey. I did a dummy booking for a train today. The cost for Zürich HB to Munich was CHF 55 with the Swiss Travel Pass and CHf 95 without any reduction. Hence, the Swiss stretch was calculated with CHF 40. A Swiss Travel Pass Flex Day (for the Swiss stretch) will cost you around CHF 77 which is a complete overkill in my opinion. You will make a donation of almost CHF 40 to the Swiss public transport system 🙂
Kindly note: other day passes than the Swiss Travel Pass (e.g. Saver Day Pass) do not qualify as discount card and their combination with international tickets is not possible.
Kind regards,
Roland