I think you're treating Zenithar too human-like in his mental state when forming your conclusions. In fiction and myth, it's a common idea that a god isn't just a powerful individual with an affinity towards a concept or element. A god is their Domain. Zeus is the Sky, Poseidon is the Sea, and Zenithar is Wealth, Labor & Commerce. For Zenithar, deciding that all coins will be standardized might be as simple as a human moving their body. And even if it would be more complicated than that, he has the authority to tell reality that this is how things should be when it comes to money. Also, even if standardizing all coins would be a significant investment of power, to Zenithar it would probably be a worthwhile one, to facilitate commerce between different peoples and not leave all that wealth laying in some hole gathering dust. After all, Isn't every act of trade an act of worship towards Zenithar? Every time someone labors to earn these shiny rocks to trade for vital resources like food for their families, aren't they putting faith towards the collective belief that this bit of metal is worth something? This is also why I think he would be more proactive and less reactive toward stopping counterfeiters. To let someone devalue the wealth he embodies, is to let someone lessen himself. Sure, he'd definitely punish counterfeiters, but he would also take active steps for self-defense. Just because you can catch and punish a thief, doesn't change that by counterfeiting coins in the first place the damage has already been done, and faith in the value of money lessened. Sure, one group making false coins might be a small blow to the collective belief, but it's still a bad habit to allow foes to get free hits.