Zoho CRM Sync Error With Zoho Campaigns on Fields Set as External ID

Zoho CRM Sync Error With Zoho Campaigns on Fields Set as External ID

When syncing Zoho Campaigns with Zoho CRM, the synchronization fails if you map Zoho CRM fields which are set as external IDs. 

So you need to either
  1. Enable the sync for these fields as well. Right now the only way to sync to Campaigns is to copy them into another field My_Field_Copy_For_Campaigns and set a workflow to keep both the external ID and its copy in sync.
  2. Remove the external IDs from the list of sync-able fields and add to your documentation that they are not syncable. 
Here was your support answer. Surfacing the issue here for the community.