I can't tell you the amount, But as a certified Small engine mechanic I can say that Kawasaki and Kohler oil both have Zink (Same oil, different label).
Short story: One Sunday I was servicing my neighbor's lawn mower and didn't have the Honda oil I normally use in low end machines, so after adjusting the valves, I threw in some Kohler oil and it was done, But was no valve noise.
Pulled the valve cover and rechecked the valve lash and it was perfect, so just chalked it up as one of those things.
The following week, I brought one of my lawn tractors to the shop, adjusted the valves, and put in the Honda oil. Same valve noise as expected. After I let it run for 30 minutes,I dropped the oil and filter and used Kohler oil and a new Briggs filter and low and behold, no noise.
The oil got rid of the noise.
At Kawasaki Service school I asked the difference between the Kohler oil and the Kawi oil they were hawking and was told the same oil, different labels but I could buy a mixed pallet of weights (30W and 10W-30) unlike Kohler where I was stuck just getting a pallet of one weight.
Now all I use is whatever is cheaper, Kawasaki oil or Kohler oil. it is the best you can get for High-temperature air-cooled engines.
Just tell people not to put it in their cars, It will poison (ruin) the Catalytic converter.
Kawi Oil is at the dealer, but Tractor Supply carries Kohler oil if you are not in the repair biz and want to buy some for your personal lawn equipment.
Since there is no more lead in the gas, the Zink is a must for the oldies like the Kohler Magnums and the old L-head Briggs and Stratton engines.
Wrenchit