Pull contacts from Hubspot

Use the Hubspot API to retrieve contacts:

https://developers.hubspot.com/docs/methods/contacts/contacts-overview

Use the RingCentral Personal Contacts API (extension/address-book) to retrieve contacts:

https://developer.ringcentral.com/api-docs/latest/index.html#!#RefUserContacts.html

See what is difference is and then use the create, update and delete contacts APIs to sync the differences.

If you would like an out of the box solution, try our partner PieSync:

https://www.piesync.com/hubspot/ringcentral/