Why would an all powerful ruler like Azkadellia need legions of soldiers?
Surely if she's so powerful shd wouldn't need them?
And why are thye armed with 20th Century Earth guns and vehicles? Where do they get their petrol from?
Also what becomes of this massive army when she's defeated? Where did Zero the loser go?
Why does any all-powerful ruler need soldiers? To make sure she stays all-powerful. The extent of her magical power is never really explored, so it's probably safe to assume that however powerful she is magically, it's not enough to maintain control without an army.
They're on roughly the same technological level as us, so their weapons and vehicles are similar to ours. They probably get their oil from the same kinds of places we do. As for what happened to them ... dunno. The movie's ending is incredibly weak and doesn't explore any of the possible fallout. Maybe the army disbanded; maybe its loyalty shifted to the new rulers; maybe one of Az's other generals took control of it and started trying to claim power for himself. Star Wars had the same problem - just because the Emperor is dead doesn't mean the Empire is dead.
Zero got locked in a metal suit like Cain was.
Cross my heart, smack me dead, stick a lobster on my head.
She's searching for the emerald isn't she? So it makes sense she'd want to have loads of people working for her out searching for it. And since she's a tyrant, she's obviously got opposition. An entire army is more intimidating than just one sorceress. If she fought all the enemies herself, she'd risk one of them possibly overpowering her. With an army, she doesn't need to fight every battle and only has to leave her castle when it's absolutely necessary
About the ending, Azkadelia is still technically in charge isn't she? She can disband her army. And if any of them rise up against her, she knows who they are and can have them imprisoned. It's perfectly likely that not everyone on her side was evil - they may have just been following her out of fear.
I'm gonna die of long hair!