My proposal:
Milano Malpensa Terminal 1 dp by train 11.22 - Venice ar 15.10
Venice - St. Moritz (Switzerland):
via Milan - Chiavenna (fastest route):
Venice dp 6.58, 10.50, 12.50; St. Moritz ar 14.51, 18.51, 20.51
via Milan - Tirano -Berninapass (most scenic route):
Venice dp 6.58, 8.58, 10.50; St. Moritz ar 17.08, 18.08, 20.08
Alternative Lake Como boat:
Venice dp 6.20 - Como ar 9.43, dp by boat 10.30 to Varenna ar 12.45, dp by train 13.24 to Tirano - Berninapass - St. Moritz ar 18.08
via Brescia - Edolo - Aprica - Tirano - Bernina:
Venice dp 6.58, 10.50, 12.50
Brescia dp 9.07, 13.07, 15.07
Edolo dp 11.15, 15.15, 17.15
Tirano dp 12.50, 16.50, 18.55 (up to Poschiavo only)
St. Moritz ar 15.12, 19.12, Poschiavo ar 19.34
via Bolzano - Mustair:
Venice dp 6.20, 8.58 - St. Moritz ar 15.58, 19.58
alternative Dolomites:
Venice dp 8.04 - Calalzo ar 10.47, dp by bus to Cortina d'Ampezzo ar 11.58, dp 13.10 to Toblach ar 13.50, dp by train 14.25 to Bolzano - Mals ar 18.55, dp by bus 19.03 via Ofenpass to Zernez ar 20.40, dp by train 21.13 - St. Moritz ar 21.59
Alternative Lake Garda boat:
Venice dp 6.58 - Peschiera del Garda ar 8.46, dp by boat 9.40 - Torbole ar 13.04, dp by bus 13.53 - Rovereto ar 14.26 dp by train 14.50 - Meran 16.44/17.46 - Mals 18.55/19.03 - bus and train St. Moritz ar 21.59
Whatever you choose, I recommend to stop over at one of the many nice places between Venice and St. Moritz.
Such a solution could be:
Venice dp 17.20 by direct train to Lugano ar 21.13. Sleep at hotel Montarina, in a silent park close to Lugano railway station (the old town center is just a few minutes away). Go then the next day by direct bus along Lake Lugano and Lake Como to Tirano and by Bernina Express to St. Moritz.
Switzerland north of the Alps:
Enjoy St. Moritz (1 day), take then the Glacier Express St. Moritz dp 9.15 to Zermatt ar 16.52. Stay 1 day at Zermatt, visit Gornergrat or Kleinmatterhorn. Leave Zermatt in the evening (17.39 or so) for Montreux on Lake Geneva (2 1/2 hrs trip). Use Montreux as a base for the visit of Chillon castle, Lake Geneva (steamboat rides), day trips to
Geneva,
Gruyeres (cheese diary, medieval town with castle, Cailler chocolate factory at Broc nearby),
medieval town of Ben and entirely walled town of Murten.
last day:
Montreux dp 8.39 by direct train to Gallarate ar 11.03, taxi to Malpensa airport (11 km), fly home
http://www.rhb.ch/Video-Glacier-eng.784.0.html?&L=4
http://www.rhb.ch/Video-Bernina-eng.782.0.html?&L=4
http://www.rhb.ch/UNESCO-Clip-eng.1061.0.html?&L=4
http://www.gornergrat.ch/home/index.php
http://www.klein-matterhorn.ch/photos/
http://www.zermatt.ch/en/index.cfm
http://www.cgn.ch/horaires/pdf/AffA2-ete-10.pdf
http://www.cgn.ch/eng/flotte
Blonay-Chamby historic railway:
http://www.blonay-chamby.ch/index-en.php
Chillon castle: http://www.chillon.ch/en/
Gruyeres castle, cheese diary and chocolate factory:
http://www.chateau-gruyeres.ch/e/multimedia/spectacle.html
http://www.la-gruyere.ch/en/navpage-ExcursionsFR-HistSitesFR-120085.html
http://www.lamaisondugruyere.ch/index.php?option=com_content&view=article&id=142&Itemid=56
http://www.lamaisondugruyere.ch/index.php?option=com_content&view=article&id=142&Itemid=56
http://www.murtentourismus.ch/en/welcome.cfm?
http://www.avenches.ch/en/page.cfm/siteetmuseeromain
http://www.neuchateltourisme.ch/en/