I have not tried it, but this guy is using it with a THETA S, which has the same API as the Z1. Use Google Translate on the article below.
This is another person that is using the THETA V with WpdMtp with the USB API.
Have you tried using the WpdMtp library with the THETA Z1 and you can’t get any connection at all?
I don’t know of any completed examples that show the Live Streaming with C#