Difference between Zscaler DC vs Zscaler HUB?

Hi there,
Can anyone clarify the difference between Zscaler DC and Zscaler HUB?
I see Zscaler has some IP subnets for Zscaler DC IPs and Zscaler Hub IPs, respectively.
But I am confused some with the difference.
What is Zscaler Hub roles?

Thank you

As per the Zscaler note -

Hub IP Addresses

For customers using third party authentication hosted by the customer (Active Directory/OpenLDAP) with ports (389, 636, 3268, 3269) or Client Autentication is being achieved via Kerberos with port 88 (TCP/UDP) and any customers or partners with Zscaler private infrastructure deployed,

And Zscaler DC IP are the proxy ip to which end user communicated for internet access.