The problem I generally have with zombies in stories is that most of them don’t have much in the way of motivation. They’re the shambling hordes. They don’t want anything (except brains, which raises the worrying possibility that the scarecrow from the wizard of oz might have been one). There are exceptions, of course. Shadow’s late wife in American Gods is one, while Mike Carey’s zombies in the Felix Castor novels are always much more individual. Anyway, a few things zombies could want:
1. To stop themselves falling to bits. The most common motivation for self aware zombies in fiction.
2. Revenge, making them essentially corporeal versions of ghosts.
3. Nothing very much, so that they are as much of a zombie now as they were when alive.
4. To get on with some work for the large multinational they work for, unencumbered by things like lunch breaks.
5. To complete their stamp collection (because zombies should have boring hobbies)
6. To have a drink in every bar in the known universe (they only shamble when they’re drunk)
7. To paint the town… um, grey, making up for all the fun they missed while alive.
8. To watch every zombie film ever released. In chronological order.
9. To achieve levels of cool normally reserved for vampires.
10. To get an official apology for the whole ‘undead’ mess out of a particularly long winded civil service department.
11. To be accepted in a wildly inappropriate job (children’s party entertainer?)
12. To go around to excitable evil cultists’ houses and explain patiently why endeavouring to raise zombie armies to take over the world just won’t work.