When I think about a tiny container of ZDDP dumped into a valve cover hole and whatever tiny bit of it making it down to the 6, 7, or 8qt pan. Then starting the engine, letting it run long enough for the oil pump to circulate and mix the oil enough to evenly mix in that ZDDP additive and of course carry the rest of it down to the pan.....
Does it sound ridiculous to you yet?
Buy the oil you need. Pour it in, start it, run it.