When using the RingCentral telephony integration in Zoho CRM, there's a free-type box where you can enter what the call was about. This text is stored in the call's Description field, as part of the Call record itself, rather than as a separate Note on the related Lead or Contact.
Beyond call notes, the current RingCentral integration for Zoho CRM covers single-click dialling, screen pop-ups showing caller history on incoming calls, automatic logging of every call, call recording and playback, and SMS sending and receiving with messages stored against the relevant Lead or Contact record.