I returned the Rotella T6 I had in the garage and bought Valvoline Full Synthetic High Mileage with Maxlife technology based on this:
https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
I've since joined the camp that believe zinc concentration is meaningless, and instead concern myself with film strength, which is a measurement of the oils ability to stay put instead of being squeezed out between the cam lobe and lifter face surfaces. Gasoline engine oils seem to fall mostly from the 80-120kpsi range, while most Rotella (and diesel oils in general) are bottom of the barrel in this metric at 70k and below.
It probably matters on high-revving race engines, but will it amount to a hill of beans for a 20 year old 4.0? Probably not, but the valvoline I bought was the same price so a little extra peace of mind isn't costing me a dime.
Its hard to find what your looking for on that page. But I skimmed through it. Some interesting information in there. Maybe zinc isn't the end all be all we thought it was.
I may switch to the Valvoline Full Syn High mileage as well. I always liked Valvoline in the past with other vehicles. I'll have to give it a try.