Lure the Zulu army into sieging your lands. Since you have higher tech, engineers, etc. you'll always be able to occupy their three (iirc) provinces before they can get all of yours. As soon as you do that, the war is automatically over. It's gamey but that's how it works.
You also want to avoid engaging with the Zulu army even if you're strong enough to defeat them. You're just wiping out your own future Soldier pops.
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