CRM Dynamics Activity relationships

Hi,

Dynamics CRM allows creating Appointments on both Account record and Opportunities record.

I am not able to create a relationship between 3 of these records due to ambiguity between tables. 

I am trying to create a report showing which accounts received appointments and displaying they City field.  But due to the missing relationship between Appointment and Opportunity, appointments on opportunities are not displaying any account data. 

Appointments have these fields:

The main relationship identifier is RegardingObject.Id

RegardigAccount.Id ( contains data if created on account object)

RegardigOpportunity.Id ( contains data if created on opportunity object)

Fields I want to display:

Account[CityCountry]

Account[isCustomer]