There are many great interviews conducted in the 1920s and 1930s with old Zulu men who were among the youngest regiments at Isandhlwana. I normally point people at John Laband's excellent Rise and Fall of the Zulu Nation as well as anything by Ian Knight whenever I see a question about the Zulu. As you are specifically asking about the Zulu view of firearms, I would suggest Ian Knight's Anatomy of the Zulu Army as well worth a read.

To give a quick clarifying statement: Many Zulu had muskets themselves, and a very few even had modern breechloading rifles. They viewed them as status symbols, and they tried to use them for supression fire on the battlefield from time to time with generally poor results. Even throwing spears were viewed by Zulu as a cowardly option in warfare, and indeed they do not seem to have been used much at all at the battle of Rorke's Drift. The short stabbing spear (assegai) was their weapon of choice and of life-long training. They were familiar with firearms going back 40+ years thanks to the Boers, but it really was not something the Zulu knew how to use well as a unit, although individual exceptions certainly existed.