Zinc Rich Oil for Flat Tappet Cams

If it works for you, thats great.

All I'm pointing out is that too much can increase wear, and in some cases, may not be compatible with an oil's existing friction modifiers and detergents.
Widman covers this in his excellent overview of engine oils, as does Grant in his review focused more on this particular aspect.
Both cite and quote primary sources relating to negative aspects of long term use of zddp above 1500, particularly these two:

“Cam and Lifter Wear as Affected by Engine Oil ZDP Concentration and Type”
Loren G. Pless, John J. Rodgers, Fuel & Lubricants Dept., Research Labs, General Motors Corp. SAE Report 770087, 1977

“How Much ZDP is Enough?” R.M. Olree, (GM Powertrain),M.L. McMillan (GM R&D) SAE Technical Paper Series 2004-01-2986, October 2004

Grant and Widman's articles are directly hot linked to pdfs.
The SAE papers cited are available only to members or by purchase. Probably also available at most engineering college libraries.

edit: @RustyRatRod While both Widman and Grant quote from the SAE papers, I think Grant has more of what your asking about.

PS. Check out this post on IFSJA with couple snips of an article from the current Engine Professional magazine. Apparently the stuff comes in three forms.
International Full Size Jeep Association - View Single Post - Our older engines and newer oil is not a good mix