Is the Zatara's logomancy being that way WOG or are extrapolating from word of god- I always saw it being like Wishcraft from Fate/Stay Night. The eizenberns had a sorcery trait that lets them substitute MORE POWER for the nitty gritty of magecraft- but it scales poorly enough, and we see few enough of them, that we don't see them pulling things like copying other magi styles with sheer power- instead they focus on physical alchemy, as a field where throwing a ton of power will leave tangible results behind, and as one that with their specialty in Homunculi, lets them create the equivalent of magical generators. Plus their big family goal is achieving the Third magic again, which as one of the effects of mastery, makes the user an infinite source of magical energy.
That went on longer than I planed but basically while the Eizenberns have the ability to just throw more power at a problem instead of developing the intricate spells to accomplish something (the whole holy grail war is a set up to leverage just enough spellwork and enough magical power so that their wishcraft (the head of the family at the time sacrificed herself to be part of the system) can make up the difference and reach the root) I always saw the Zataras as basically having a similar shortcut.
TDLR i don't think the Zataras do the backwards talk because they know JUST SO MUCH about magic, but because they have a bloodline given ability that lets them substitute the backwards talk for other spellwork- ie Talking backwards instead of invoking gods or making ritual circles. And like the Eizenberns their are limits to it, probably in terms of knowledge and practice or else they would be gods that could backwards talke their way into anything.
I think it might depend on how exactly Grundymen work- my guess is that the souls don't leave the body properly- heck the whole practice might exist due to whatever Melmoth did to make a zombie new god work- ei blocking souls from moving on.
The issue is surviving removing a ring long enough to hand one over, and since his other sword just won't work since the zomgod only has one, there is the risk that the god magic might consider it uneven if the remaining implanted ring is implanted instead of worn like the one he could hand over. So he has to risk cutting open his chest to remove that ring and hope the one in his skull will start working so he can survive that, and at the moment he is stuck in his armor in the middle of a fight so he can't stop to carefully do self surgery.
Also has melmoth stoped talking or is Paul's muting him still working indicating that ring functions not aimed at making the fight uneven might be working-
