How do I change what value that the Lookup field shows in the autocomplete view?

As far as I can see only the Lookup Module's primary field is displayed, and there is no way to change it.

Currently I'm testing Zoho CRM for a klient and trying to make a use case work.

I have two custom modules.
One is called "DevPostnumre" and has the Primary field configured as Auto-number.

The second Module is called "DevHusstand" and has a lookup field pointing to "DevPostnumre" (postnummer).

The autocomplete list displays only the Primary field auto-number value which, in this case, to useless. 

I would like to change this behaviour to show the "Single Line 1" field in the screen shot above. 

Is this possible?