Ok impossible to take the gold or diamonds without crush the Zulus and then annex their country , but there were about gold and diamonds in Zululand ?
If so, how could they know, since the Zulus had no mines of gold or diamonds and that no whites were sought in Zululand for that ?
the invasion of Matabeleland for gold or diamonds, it's Ok, but for Zululand, is another matter ...
The idea is that Frere wanted to create a confederation or a federation and make it safe from Zulu, crushing, and then annexing them is more realistic.
Cape Colony + Natal + Transvaal + Zululand = South Africa dreamed by Frere ...