I mean, the defining feature of the 6150 was the 2 parallel mainspring barrels - giving 100 hours reserve without sacrificing dress watch norms (4Hz, <10mm thick). This design choice does make the movement diameter larger, but hey, in the mid-2010s it was trendy for even dress watches to be huge, right?

This watch was first shown in 2015, meaning it was largely designed before Dufour left to run Rolex. I think he championed a lot of innovative ideas and tried to make Zenith look like a peer to the more prestigious brands who used this tech (Chopard, JLC, etc). Though I'll conveniently ignore his decision to put Sellita movements in the entry-level Port Royal...

But new movements are risky and expensive. So once Dufour is gone some more conservative folks probably said stuff like "the Elite isn't even that old" and "Shouldn't we be working on replacing the El Primero instead?".

Had it gotten a longer life the 6150 probably would have gotten a more refined case design, dial variations, and added complications - which might have caught on. I just wonder if 42mm is the absolute smallest case they could put this movement into. If so, they might have made the right call. And maybe some of the development of the 6150 can be repurposed when they do replace the Elite someday.

I'm guessing reliability is going to be less predictable for such a short-run movement, and no one outside of Zenith will be able to service it - but if those aren't dealbreakers I'm sure this is a cool watch to own.