It is hard to say, probably Filoni for me. However, I gotta take this chance to echo a sentiment you expressed about Zahn. I actually prefer the new Thrawn trilogy, but what you said about him writing the force weird is a thought I have had for awhile.

I would have to look up the paragraphs I have written about rhis before, but essentially I feel like makes a very interesting (whether good or bad to ya) move with the force that is very seldom discussed. He kinda puts tactics and evolution above the force and spirituality. Ysalamiri evolve to repel the force or whatever right, and that is a very strange notion. He explicitly mentions evolution more than once (ysalamiri and the invisible alien from I think the second book?), which I never expected a Star Wars book to for some reason. Force ghosts basically die/fade eventually if I remember correctly the opening of the trilogy. Thrawn is beaten not because of some spiritual connection, but because of a tactical error he makes in the second book. Force users like C'Baoth are countered with stuff like droids IIRC, with stuff outside the force instead of like something through the force.

There are a few other things, but it just seems clear his books do not revive around spirituality or anything, it all about the head game and out-maneuvering. That is normal for a book focused on soldiers, and weird when Luke is a main character IMO. Normally, what a writer does with the force is expand it right? More powers or more spiritual and moral depth, that sort of thing. I feel like Zahn makes the world bigger by saying there are things bigger than the force, like evolution and cunning. Can you imagine if the ST, which the og Thrawn Trilogy is supposed to serve as according to many, made that sort of implication? It would be so profoundly strange of a shift and I think a lot of fans would have much mroe mixed feelings on it. I kinda respect it, it's bold and different, but it 100% is not my cup of tea. To be fair, this was written when all we had eas the OT, I feel like things were a little less locked in place then. I never felt like Star Wars was really focused on the tactics of wars, but it's not completely out of left field. Maybe that is what Zahn was seeing and appreciating primarily in the OT at the time.

Hopefully what I am saying makes sense enough, I am going off of a somewhat hazy memory.