Which Major Privacy Coin Primarily Utilizes zk-SNARKs?

Zcash (ZEC) is the major privacy coin that primarily utilizes the zk-SNARKs cryptographic proof system. Zcash offers users the option of "shielded" transactions, which use zk-SNARKs to fully encrypt transaction details on the public blockchain.

Users can also opt for "transparent" transactions, which behave more like Bitcoin's pseudonymous transactions.