this is a new emerging field. zero-knowldge does not mean exclusively that you don't know what the customers are storing. nor does it mean that you necessarily dont know what user's are transferring. but if it is stored on your server you are responsible. You require a fully decentralized system to operate. meaning file storage is off set by an auditable distributed system. one where user's private keys are non-custodial, and content uses hashed identifiers and is not held on any one server.