Wouldn't it be too dangerous to use silver zinc batteries?
Source wikipedia:
Silver oxide batteries become hazardous when they begin to leak which generally takes a period of five years (which is their normal life) from the time they are put into use. Until recently, all silver oxide batteries contained mercury (around 0.2%). The mercury is incorporated into the zinc anode to inhibit corrosion in the alkaline environment. Sony started producing the first silver oxide batteries without added mercury in 2004. [6] Most jewelers and watch makers leave these batteries in an open container in their shop, which could lead to health problems for the jewelers. If they do not retain them, they usually discard them in the trash which causes many environmental problems. Once the battery is spent (dead) it needs to be properly handled and recycled by an authorized recycler according to the EPA's Sector of Waste Wise, a program that sponsors correct ways to recycle silver oxide batteries.
Did you miss that the ZPower are Silver-Zinc batteries, and maybe these "dangerous" silver oxide batteries are something different? I doubt ZPower would get all this "green love" if they were hazardous.