OCI is a standard that supports layers (and cache thereof), hashes and has a verified way of sharing (via OCI image registries).
A .zip is much more monolithic, and there are no ready-made .zip registries you can upload your .zip to that will automatically checksum it, or allow it to be delivered in layers (and skipping the layers already present on the registry/destination).
A .zip is much more monolithic, and there are no ready-made .zip registries you can upload your .zip to that will automatically checksum it, or allow it to be delivered in layers (and skipping the layers already present on the registry/destination).