Zanac is the Second Prince of Re-Estize Kingdom, son of Lanposa III. He is the younger brother of Barbro and older brother of Renner. He is described as a short and fat man.
He is described as an incompetent person, but is actually quite sensible, capable of comprehending the true natures of Renner and Marquis Raeven. Zanac is aiming for the throne and as such wants to remove the first prince from the line of succession.
(Source: Overlord Wiki)