There is a choice of three mountain passes to eastern Switzerland from Zürich: the Flüela, the Albula and Julier. The Albula drops you close to Zuoz, the Flüela is more convenient if Scuol is the destination and the southern-most, the Julier, is close to St. Moritz. From the standpoint of scenery we prefer the Flüela.
Using Die Generalkarte #1 and #3 for Switzerland, take the autobahn N3 southeast toward Chur. In winter or early spring stop at Heidiland autobahn rest stop where the Graubünden tourist information counter can tell you which passes are open.
Exit the autobahn at Landquart and follow Red Road #28 toward Davos. Before you have gone very far you'll see a sign indicating whether the pass is open or closed. You'll go through Schiers, Klosters and the outskirts of Davos, then over the pass. After that you will come to the intersection of Red Road #27. You can go left to Scuols or right to Zuoz. Via the Flüela the trip from Zürich is about 195 km/120 miles.