In my opinion, the Interior Green was darker, and the green had a bit higher saturation in the green compared to Zinc Chromate.
I got a neat deal on some ZC many years ago. I worked at McDonnell Douglas in STL. Word got around that a local surplus store had a great deal on ZC primer. Turns out that Mac had ordered a big shipment of spray cans for touchup work. But receiving inspection declared the color was off a bit, and the whole order ended up at the local store at a really cheap price. I picked up four cans. Was working on a 1:1 plane as well as models.