Question: Can I change from one custom domain to another without experiencing downtime?
Answer:
At this time it isn’t possible to migrate from one custom domain to another without a disruption. This is the result of not supporting seamless migration of custom domains at this time.
If this is something you believe would help you in the future, please share your use case with Auth0: Secure access for everyone. But not just anyone..
Supporting Documentation:
Documentation: Custom Domains