I wouldn't think that Dexron VI is "the same" as Mazda's blue ATF-FZ although it might work well enough.
If I were going to use anything other than OE it would be Maxlife which I believe claims to work in the Mazda application.
Here's a thread that might help:
Use Mazda OEM ATF-FZ, get it at the dealer. I did a drain and fill on our CX5 a year ago. OEM fluid is not cheap. The only other alternative is Ravenol ATF-FZ but I never tried it.