If you're going for an ideal, you'll want to use a break-in oil, with the zinc already blended into the oil.
Some sources suggest adding the zinc (such as ZDDP additive) to standard motor oil does not protect the camshaft on initial startup as well as the pre-blended (with zinc) break-in oils.
This is because the zinc additive and standard oil mix, more or less, only after the oil has been heated by the operating engine and the oil "stirred" by several cycles through the oil pump.
Break-in oils are heated and blended prior to bottling. Vintage motor oils contained more zinc, lead and cadmium than the healthier, more environmentally-friendly motor oils do modern-day. I believe it's generally accepted the synthetic oils modern-day contain very little of these lubricating heavy metals.
The zinc (and those vintage heavy metals) benefit the camshaft and lifters best during initial startup. You want that zinc doings its best to bond with those surfaces, lubricate and minimize wear on the first few revolutions of that initial engine startup and break-in.
By the time a ZDDP additive is sufficiently blended to provide ample zinc to the lifters and camshaft, some minor wear (that may have been avoided with a pre-blend) has already occurred.
Presuming this is all true, I'm not sure it really matters. Breaking in an engine involves, more or less, wear on the engine. Wear to hone and fine-tune microscopic roughness into smoother operating surfaces on the rings, cylinder walls, bearings, lifters and all rotating and moving surfaces.
Gosh, I seem to recall several stories from days past of breaking in engines by starting them up, and immediately running some quarter mile runs to "seat the rings" without much concern for scored camshafts, failing lifters or placing too much wear on bearing surfaces.
