Err, was the name messed up in any other publications? From comic books and trading cards I had at the time, I only remember the action figures making this mistake. Everywhere else Zuckuss was the guy in the mask and 4-LOM was his droid. A name like 4-LOM being numbers and letters seems like a very droid like name, so it stands to reason that it was intended this way and Kenner just make a mistake.

Also, judging by the fact that Kenner later corrected the mistake, I'd take this as overwhelming evidence that the names were in fact mixed up, and not just a change forced on us after Star Wars "turned bad".