Why is Zion built on Lightning, instead of another blockchain?
The innovation of the Lightning Network is the use of time-locked transactions and cryptographic nonces to allow many two party payment channels to form a connected network where payments can be sent over many channels without trusting the intermediate nodes. The topology is similar to IP networks (the internet): packets of information are routed over many physical links, and the communicating end nodes don't worry about the route as long as data gets to the destination. This works via a decrementing time lock that permits every intermediate node along the routing path to accept funds only if they forward it along to the next participant, using disclosure of pre images of cryptographic hashes. In the Lightning Network, nodes are not able to seize funds traveling through their channels even if they fail to forward payments or refuse to perform any actions. A node operates without custody of third party funds, which is enforced by a time limited cryptographic script. Zion uses these same cryptographic functions to move data across the same packet layers.