If your soil is low in zinc, then even plants that accumulate zinc may not be able to help.
I agree with this. I hear so many people complain that their soil is lacking a nutrient, and want to find an accumulator to gather it. Dynamic accumulators cannot manufacture nutrients. They can only gather what they can find, which in a deficient soil may be
zero. To gather any zinc, you would probably need an accumulator whose roots go deeper than your pecan's roots do. Most zinc accumulators are also trees - shagbark hickory, black cherry, red cedar, indicating that most zinc is probably no longer near the surface. About the only non-tree plant that that I know of that may help is the Coneflower
Echinacea spp.
I get radically different numbers from different sources, ...
Once again, a radish grown in a zinc rich soil will have much higher numbers than one grown in a zinc poor soil. Nutrient densities in plants have a direct relationship to the nutrient density of the soil in which they were grown in.