Following the record

I wonder if Zoram felt a connection or responsibility for the brass plates. Was that the thing he was most passionate about in his role as keeper of the treasury in the house of Laban?

It is entirely possible that he was not a free man in the household of Laban and he might even have sought out his position out of a desire to care for the sacred record. Perhaps he was willing to go with Heidi partly because he knew that regardless of his choice the brass plates would remain with Nephi. Also, with Laban dead and the record gone Zoram might have been at risk as a prime suspect in the death and apparent robbery.