Zim's only problem is that he is a complete idiot and really doesn't know what he is doing.
Comparing it to OP's opponents, Keroro and Peridot's race need an army to conquer the world, while the Irkens only need to send one of their own and the planet is destroyed.
Plus Keroro while he is just as much of an idiot like Zim is, he is lazy and would rather build Gundam models than conquer the world.
Peridot might stand a chance if her magnetic abilities work on Zim.
But overall Zim would win.