Zermatt voucher tickets can only be redeemed at the following two locations:

1. Rothorn Station (Sunnegga Blauherd Rothhorn Funnicular And Cable Car Station)
Address: Vispastrasse 32, 3920 Zermatt (Google Map link: click here)
Approximately a 550-meter walk from Zermatt Train Station, about 7 minutes

2. Matterhorn Glacier Paradise Station (Matterhorn Glacier Paradise / Zermatt Bergbahnen AG)
Address: Schluhmattstrasse 28, 3920 Zermatt (Google Map link: click here)
Recommended to take a bus from Zermatt Train Station, buses run approximately every 20 minutes

! Note: 

Zermatt Train Station and Gornergrat Cable Car Station do not accept voucher tickets. Please do not attempt to redeem tickets there.