Playing with zombie mode, if I'm lucky the city state that lets you choose your prophet's ability is in the game (Laventa? I forget which one). I pick convert barb's. then I park the prophet until I'm about to get overrun by zombies, then I pop the prophet into the middle of a zombie cluster. Instant zombie army. If I'm lucky, my prophet will have extra charges to use. Later in the game I combine zombies into armies, at least that way I can protect my cities. By that point all of the AI's are usually down to just a capital city surrounded by zombies. I slip a prophet into the zombies next to the ai city, pop them into my soldiers, take ai city in one turn as the zombies will have already took out the walls. Yeah I don't do zombie mode too often, mid to late game zombies are brutal.