Is zkSync a Starknet?

Could you please elaborate on whether zkSync is considered a Starknet? I'm interested in understanding the relationship between these two platforms, if any, and how they might differ in terms of functionality, use cases, or technological architecture. Could you also explain what zkSync specifically offers that might distinguish it from Starknet or other similar projects in the cryptocurrency and finance space? I'm looking for a clear and concise answer to help me better grasp the nuances of these technologies.