Plan A:
St Moritz - Zermatt by glacier Express ( I need to buy a spread ticket for this, if i got swiss pass?)
For the Glacier Express you must reserve seats in advance and you should reserve seats for the whole journey from St. Moritz to Zermatt. You have to pay extra for the seat reservation. SwissPass rail passes are valid on this train.
InterRail & Eurail passes cover the Rhätische Bahn (RhB) between Disentis and Chur, but not the Matterhorn Gotthard Bahn (MGB) between Zermatt & Disentis, so a separate ticket is needed for this section, in addition to the Glacier Express supplement. This extra ticket costs about CHF 80 - you can check this price at www.sbb.ch, just ask for the 2nd class fare from Zermatt to Disentis. You can buy this at any Swiss station before you travel, along with your Glacier Express supplement/reservation.
Note that you can also use cheaper local trains and get the same view.
Plan B:
(What mean is paranomic Golden Pass?) This journey need to pay extra $ for ticket?
GoldenPass is the name of a train that goes from Zürich - Luzern - Interlaken - Montreux to Genf. The word "panoramic" refers to the panorama wagon that is available to 1st class passengers on this train. Eurail and SwissPass rail passes are valid on this train, don't know about Interrail.
http://www.goldenpass.ch/default.asp?Language=EN
Zermatt -Venice by train
Vernice - Pisa by train
Pisa - Rome by train
Buy 2 tickets in Zermatt:
- one to Venice
- one from Venice via Pisa to Rome with regional trains
International ticket with regional trains is the cheapest way to travel in Italy.
For Switzerland check prices using
http://www.glacierexpress.ch/
http://www.goldenpass.ch/
http://www.sbb.ch/
and add everything together. Compare with the price of the Swiss Flexi Pass. The Swiss FlexiPass for 3 days is CHF 249.00 CHF per person, if you buy 2 passes you get a discount. It will then cost you 211.65 CHF per person.
Since you are using the Glacier Express both in Plan A and in Plan B it will likely be cheaper to use the Swiss FlexiPass than to buy a Eurail or Interrail pass.