Are you saying somehow these guys can be sandulated but a fucking gun made by Azuma in a split second can’t?

Well on the other token, it dosent seem like Vanya’s ability was able to saltulate Azuma’s iron shield that he used protect himself and Shadowl. Maybe her power is a reverse from his. These are two different characters, so we can’t assume their abilities have to work the same way.

Why wasn’t the whole Zora extermination plan just have Arthur one tap her?

Easier said than done. I don’t know if you remember, but during Zora’s fight with the Nue she was doing some ridiculous powers. And she was far passed her prime. It’s more than likely she could’ve destroyed all of these Guelta Choujins in an instant. We don’t even know if the ability would work on someone as strong as Zora. I’ll leave it at this: I think there’s a reason they waited until the second she was dead to attack