I definitely want to talk to them, it seems they would make a good addition to the NIWA resource pool. There's a bit of overlap in content coverage, I just browsed their Zelda stuff, but most of it is characters and games. ZW covers everything else like places, items, weapons, etc. Of course if they are willing to join us I wouldn't request they purge those pages or anything. I think a sweet deal could be made, for instance: to just link to ZW in Zelda articles, and ZW link to them for anything that's currently being linked to Wikipedia. That way everybody keeps their content and is happy.
It seems this is very fitting of the description of a potpourri wiki we discussed which would cover EVERY Nintendo game, (Nintendo as a publisher, not as in everything playable on a Nintendo system fyi). Of course we all know we offer them a much larger user base and shared technical expertise.
Update: I just sent one of their active staff members an overview of NIWA and my contact details. I figure to talk to them to gauge their interest, and any decision would be made in the private boards here.
Edit2: I unlocked this in case Masamune wants to talk about GameHiker in here.