If you have a stock motor with a stock cam or close to stock cam there is adequate ZDDP in the current SM rated motor oils. It's when you start using a high lift cams with very stiff springs that the level of ZDDP in SM rated oils becomes questionable.
Of course this only applies to flat tappet cams, roller cams its not an issue. And its always a good idea to break in a cam stock or otherwise with a break in additive that has addtional wear additives.