Zakzak Stronginthearm is a Dibbler-like purveyor of suspect magical merchandise at inflated prices for gullible young witches. He is a dwarf and most of his stock has little or no magical value, but but it looks impressive. It is, in fact, this high Boffo-quotient that has provided him with a very good living: the stuff doesn't have to have any intrinsic magical value provided it looks good and shouts "Witch!" Zakzak has in fact hit upon a sort of recipe for the Philosopher's Stone, that which turns rubbish into gold. He has discovered what drives adolescent girls: the peer pressure that causes young girls to conform, find a place to be cool in among consumer goods which can be perceived as cool.
He works with Brian, his supposed Wizard adviser. He actually does make very good knives. Business, as of The Compleat Discworld Atlas, is booming: Zakzak has opened a second store in Sallet Without in Ankh-Morpork.
And the dwarf selling those desirable consumer goods in the perceived cool hang-out has indeed found his own goldmine. Had Zakzak been born on Roundworld, he would surely have copyrighted the idea of "Claire's Accessories", a store where put-upon parents of adolescent girls hold out wallets and purses to be emptied, on the grounds that giving in is easiest.