Part of the Zulu war plan is to create a "Sphere of Control" (well, oval). This is the region that contain luxuries, and would give us a monopoly on the gems later. This region is from New Hlobane, New Swazi, and New Ngome down south to Coyotepec and Allegheny. (We could pick up Grand River, Salamanca, and St. Regis if it doesn't put us over the domination limit). This region (Gem Mountain II), would give us the monopoly we need for any final trades.
The Zulus also don't have rails, so we could let Persia attack the Zulus in the north, and build rails for us.