That's not a typo; I do mean "zinced," not "zinked." And, right up front, for chocolate aficionados, "zinced chocolate" may be quite tasty, but not necessarily something you really need, despite some purveyor's claims of potentially prolonging life, slowing-down the aging process, preventing "oxidative stress," and other benefits.
The word "zinc" is simply the English spelling of "Zink" that is derived from the old German term "Zinke" that refers to the metal's jagged crystals. More information on the etymology can be found at Wiktionary. Just to explain the difference between zinced and zinked then, let me briefly refer to the latter.