I know this is not the answer you are after, but there a big chunk of south america where Zika is not an issue.
Within south america, the biggest concern of Zika is Brazil.

Anyway, you can redeem your Travel Voucher online. IIRC, on step 4 of the purchase process there will be an option that says "I have a travel voucher" or something like that. Travel vouchers are usually linked to the ID number of your travel document at the time of compensation.
If you can't get it to work online, you can use the Travel Voucher and make the purchase over the phone.

I don't remember if you could exchange your Travel Voucher for cash so many months after the fact (I think you can, although it depends on where you were awarded the voucher IIRC). Do keep in mind that travel vouchers are not exchanged for cash at face value. Tipically, if a travel voucher is worth USD 800, you'll only get half that amount if you opt for a cash compensation