Thank you very much for your question.
A point to point ticket is a ticket valid only on the selected route, from A to B. You can take any train on this route and make stops in between, as long as you resume and complete the journey in the one direction (in this case from Zürich Airport to Zermatt) by the end of the validity day (5am on the following day).
A Saver Day Pass is a day ticket valid everywhere in Switzerland for a whole day (until 5am on the follwing day). This means you could go form Zürich Airport to Zermatt taking any route, because on that validity date you have a pass for the whole country (GA area). If on your wish date this is the cheaper option, I suggest you buy this offer.
Please note, there are also Saver tickets: those are like point to point tikcets (fix route) and also fix in time, it means, if you chose the connection at 10 am, you cannot get an earlier or a later train.
This porobabily is the least expensive option, but I would not recommend it when arriving by plane (because teh landing time can change).
Both Saver day passes and saver tickets are non refundable.
I wish you a good stay in Switzerland.