I've read a LOT, believe me. And while there's no doubt about the science of zinc and wear, there are no statistics about real-world results from modern engine oils. Lots of stories about "no zinc killed my engine" just like my stories about "no zinc had no effect," but there isn't any science about increases in oil-related cam wear since '94, when they started decreasing zinc content in automotive engine oils (the adoption the API's SH designation). Twenty years of Camry owners going to Jiffy Lube and never having heard of ZDDP seems like the potential for an entire industry to spring up making camshafts for Camrys... and it hasn't happened.
There was an article in some automotive trade magazine I read a few months ago while getting my car smogged, suggesting that the effects of zinc loss have been far less than expected. The article attributed the fact to the nature of the problem in the first place: Zinc is primarily a consideration during initial start, before oil is flowing through the engine and there is abnormal metal-to-metal contact. Once the engine is running, the usefulness of zinc more or less disappears - or, at least it should.
If you do a lot of short trips, with lots of stops & starts, no zinc could be a significant problem. But for most people who starts their car maybe 2-3 times per day on the outside, engine start damage just doesn't add up to much over the lifetime of a car. Using a quality oil of a proper viscosity for the climate plus a quality filter with a lasting anti-drainback valve mitigates the cold start problem significantly - so perhaps that is in play with my engines as well.
On the other side of the equation - opposite the "more wear" concern - reduced zinc levels improve catalytic converter life and reduced phosphorus limits carbon buildup in bores and valve trains. Those are definitely desirable.
Bear in mind I'm talking about not-new, stock engines. For breaking in an engine, I'm 100% behind adding zinc. There is a lot of potential for wear there and zinc will mitigate that. For a high-po engine with stiff valve springs and high lift where that cold start period can truly be hell, zinc makes sense as well.
But a stock motor with squishy springs and sane lift, there just aren't any statistics that I have found to support the idea that zinc is actually all that important. If you've found some, I'd love to read them. But I've tried & failed.