I believe the normal Zabuza can be useful in some specific scenarios, like Ninja Exam for example, where he can blind the enemy team (which they usually hit like a truck and have bloodlust passive).

I don't find the 7 Swordsman one to be that useful at all. There are better options than him in pretty much any team. He's like a little bit of control/damage, but excels at neither. If you want control, Shikamaru is better. I'd rather run Suigetsu if you want the same chase, but more damage.

Normal Zabuza, however, can have his use for Ninja Exam as I don't know of that many ninjas that can cause blindness to an entire team. Who knows what event/instance/future update might require a ninja that can blind. He's not great, but he's got more uses than 7 Swordsman Zabuza, in my opinion.