That's odd. In general, an integration between two platforms using Zapier works like this:
Platform 1 <--> Zapier <--> Platform 2
Where each platform creates it's own app on Zapier, and manages how the data is passed between their app and Zapier (and vice versa). In this specific case, the structure would look like this:
HubSpot <--> Zapier <--> Zoho
We have our own Zapier app that we manage, and (presumably) Zoho manages their own Zapier app as well. While I'm not entirely familiar with Zoho's side of things, it sounds like they might be referring to their API endpoints for different data centers? (see below) This would be something that Zoho would have to configure in their Zapier app; it's not something that HubSpot would be able to change on our end.
I hate to send you off back to Zoho, but I think you'll need to contact them asking for more information. If they have specific information about what needs to be changed/configured on the HubSpot side, please don't hesitate to reach back out on this topic and we can work through it. Otherwise, they'll likely need to correct the API on their end.