One simple application is making blockchains vastly more scalable. For a blockchain to be secure you have to store each transaction on chain, with enough infor

One simple application is making blockchains vastly more scalable. For a blockchain to be secure you have to store each transaction on chain, with enough information so everyone can verify that it's valid. Normally this means storing the sender's signature, which is bulky. With ZK, you can bundle up thousands of transactions, skip all the signatures, and include a single 256-bit proof that all the transactions had valid signatures.