I just finished cleaning my plane with mineral spirits followed by hand-application of Zephyr Pro40.
This picture is my plane after the last time I polished it with Nuvite-C grade in November 2017:
And this is my plane after today (May 2020):
I think the Zephyr product does a fantastic job of restoring a 2.5 year old polish job with a lot less work. It doesn't really make it look BETTER than a full polish job, but it absolutely worked as a maintenance polish. Might have bought myself another year before breaking out the Nuvite and pads to clean up all the water spots (I'll try Zephyr with a buffer first.) It did remove fingerprint marks.
Just to re-iterate, Zephyr Pro40 did nothing to improve the shine of non-Nuvite polished parts on the plane (though it did clean them up a bit), and I don't think it replaces Nuvite (or other similar initial-cut polishes) for the original polish.