The result of your conversion between zeptojoule and grain/gallon [US] appears here
To convert between Zeptojoule and Grain/gallon [US] you have to do the following:
First divide 1.0e-21 / ((0.45359237/16)*(192/175)/480)/0.0037854118 = 0.
Then multiply the amount of Zeptojoule you want to convert to Grain/gallon [US], use the chart below to guide you.
Symbol: zJ
No description
Symbol: gr/gal
No description