Granular aluminum is a very active reducing agent, especially when hot -- this is what drives the Thermite reaction.
Many chlorinated and fluorinated/chlorinated organic compounds come with warnings not to let them contact aluminum. This is because aluminum can react with these compounds to generate aluminum chloride (AlCl3) -- a powerfully reactive Lewis acid -- and a (at least partially) dechlorinated organic compound. In the case of hexachlorethane (HC) one would expect the first product of reduction to be tetrachloroethylene (TCE), a toxic, carcinogenic liquid which is reportedly able to react violently with aluminum. The reduction product of that *might* be, but probably isn't dichloroacetylene, a gas with reacts explosively with oxygen; it's more likely that in the presence of atmospheric moisture it is reduced to trichloroethylene (unfortunately, also "TCE" ), a toxic, carcinogenic liquid made infamous by the high incidence of leukemia in the vicinity of chemical plants in Woburn, MA, publicized by the book and movie "A Civil Action". None of the compounds listed so far should be ingested by anyone.
So what's all the emphasis on zinc chloride ? Zinc Oxide (ZnO), a slightly basic oxide, is capable of reacting with the more acidic AlCl3 to form ZnCl2, a weaker (but still irritant*) Lewis acid, and Al2O3, which causes Shaver's Disease when inhaled. Calling this mixture a "toxic brew" isn't hysteria or overreaction, it's a pretty straightforward literal description. Supposedly, these "smoke grenades" were declared obsolete years ago. It should be illegal to keep them around anymore.
*If you've ever done soldering with an "acid flux", you've probably inhaled a little ZnCl2 and the HCl fumes that accompany it. Not particularly pleasant, but maybe one of the *less* harmful chemicals in this "green smoke".
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