Unfortunately, you cannot join the related tables just like that with audit table. Moreover the query may need UNION to join based on objecttypecode with different tables. FetchXML does not support UNION.
The audit table is little tricky, it is not like any other entity - as some of the data is stored in denormalized and delimiter separated values in columns like changedata. Also relationship is not maintained between audit and other tables other than systemuser. Read more

You can play around the audit table using XrmToolBox FetchXML builder and observe them.

Web api endpoint for audit entity is below:
https://crmdev.crm.dynamics.com/api/data/v9.2/audits?$top=50&$select=_objectid_value,attributemask,operation,transactionid,useradditionalinfo,createdon,_userid_value,_regardingobjectid_value,objecttypecode,action,auditid,_callinguserid_value&$filter=objecttypecode eq 'account'
Very interesting part is $filter=objecttypecode eq 'account' in above web api query. I don't know how is this even working. This is contradicting between web api and fetchxml.