For more details on the listing tiers, please refer to Listings Review Criteria Section B - (3)
Zerochain is basically designed to store encrypted data. Usually, all data on blockchain is public and everyone can see it, while the data on Zerochain is encrypted so that no-one can see the data without the key for decryption.
Zerochain is built on Substrate which is the blockchain framework developed by Parity, and also using the bellman library developed by Zcash for zero-knowledge proof system.
In the future, Zerochain would work as a privacy-preserving blockchain connecting to Polkadot network.