Just read this thread about skipping clutches with the stp zinc. Wish it was posted sooner, my clutch just started slipping a little.
I too would love to see a list of oils with good amounts of zinc!
Lately this has become a short list, thanks to the EPA.
The ones I have found that have it now are: Bel-Ray Mineral oil and Amsoil's Motorcycle Oil (not their "V-Twin" oil). The Valvoline Motorcycle oil (also not their V-Twin oils) has some, not quite enough: I used it successfully a year ago, but added some zinc to make it shift smoother, too. The gearbox appreciated the zinc noticeably in that oil change.
Generally, diesel-rated oils and/or "offroad rated" oils are the bare minimum needed today for these bikes. These oils have a little zinc still left in them, and certain viscosity chain enhancers that improve their cling performance when hot. Diesel-rated oils come in 15w40 (useful for the smaller Fours) in most auto parts stores, and if you look long enough you can find 20w50 (the 750 especially needs this for long life).
The Castrol 4T is about the same performance, in my experience, as the Valvoline, but will not attack the rubber seals like the Valvoline does (after lots of miles). Today, it is missing most of its zinc, so add some if you use this type. I use this for many bike break-ins after rebuilds, as it costs less than the Bel-Ray or Amsoils.
If you can find it where you live, Torco makes a good oil in 20w50 for the 750, too. Their "offroad" version still has good zinc, too.