What Charles and I are saying is to use the right oil to begin with,...
IMHO, ZDDP additives are justified for initial engine start when new and during the first 3-4 critical hours of running-in. Beyond that, simply adding additional ZDDP without a corresponding correction/change in the detergent package is asking for trouble and NOT advisable.
There are really good reasons for how the chemistry gets balanced in those oil formularies.