How do you map a user picklist field to another user picklist field.

How do you map a user picklist field to another user picklist field.

In Zoho Projects, I'm trying to map a custom field (user picklist) in Task Details to a field (user picklist) in the Project Details. How do you get the two to map to each other?

This is what I currently have that works for my other fields but doesn't work for the user picklist: 

params.put("custom_fields",{"UDF_USER1":ManagedBy});

When I do a direct mapping I get this error:

{"error":{"status_code":403,"instance": {"message":"Data type mismatch","field_name":"UDF_USER1"},"title":"INVALID_PARAMETER_VALUE","type":"FIELDS_VALIDATION_ERROR"}}