After an hour of focused listening this morning, I can confirm the Auteur constitutes an end-game pairing with the ZDS. I'm not sure what this means for the Utopia at this point. I'll probably end up keeping both, as it's likely no other existing dynamic driver will displace the crystal-clear transparency, stat-like speed, and explosive dynamics of the Focal. In terms of the Auteur, I have never experienced this kind of natural timbre from a flagship headphone before, the closest perhaps being that of the HD650/HD600, but those are not flagships despite their scalability. There is a very pleasant sense of reflection from the blackwood, but the background is so black, and notes seem to just pop. I appreciate that these are more closed than what I am used to for this reason. Resolution approaches that of the HD800 and Utopia (this is hard to quantify, and I need to listen more to where exactly in the FR this is happening), and I can see why people have made the comparison of marrying the best attributes of the HD800 and HD650 while advancing its own unique qualities.
If only today wasn't going to be 97 degrees Fahrenheit and humid. Not the best climate for a ZDS to be running all day!
I usually like to spend days/weeks before drawing conclusions so as to avoid bias from new-toy syndrome, but perhaps because I have been trialling more headphones recently, I am confident these are keepers.