Zeus sends his lower-ranking representatives, such as Power, Hephaestus, and Hermes, to do his dirty work for him. As a result, Prometheus is forced to dish out all his rage against people he doesn't even respect that much as enemies, because they aren't the boss man.
Just one more frustration for Prometheus to dwell on.
Well, obviously. Zeus is the one giving the orders; he's the Big Bad whose rebellion got him power in the first place. Funny, you think he'd be sympathetic.