Nissan(jatco) has issues with zinc. As long as it is a newer DexronIII equivalent, you won't have problems. Low ash in this situation is zinc free! And, Nissan has a TSB on it.
If you look at the UOA section, you wont see any ATF's with a zinc addtive(exception Honda).
"ASH" in the automotive sense are the solid materials left behind (in this case, mostly metals and hydrocarbons) as a result of combustion, and is mainly used in connection with combustion of fuels and oils.
The more accurate term for ATF lubricants would be "low metallic content" ATF's since we don't burn ATF in the combustion chamber.
As unDummy stated, most ATF's, use low levels of zinc, calcium, and sulfur to keep the porous cluch materials from becoming contaminated with the wrong materials.
Now Honda Z1 is an exception since those tannies have been descibed as automatically shifted manual transmisson, and therefor contain moderate levels of ZDDP or zinc components as AW and antioxidant additives.
Calcium is used as a rust preventative, and very mild AW additive, while Boron is used as another mild AW additive and tbn adjuster.
The main AW additive is a mild phosphorous/sulfur combo, but sometimes a "phosphorylated boron" is used to provide a triple play as a dispersant/AW additive/tbn adjuster.
As you can see from this:
Boron is an element that is in between a pure element and a metal but and is not considered a metal.
Besides, calcium and Boron are used at low levels.
Some times you will find traces (5 to 10 ppm) of zinc used as antioxidant.
However, zinc antioxidants are being replaced by modern antioxidants which are non-metallic.