We are in danger of starting another "oil thread"
The issue with zinc is, that automotive spec motor oils have a significantly reduced ZDDP content, which is bad for all motors with flat tappets (non-roller lifters), which includes most (or maybe all) motorcycles.
You need to use a motorcycle specific oil or an oil with a ZDDP of 1200ppm or more. Mobil1 20W50 used to have that, but I cannot find this anymore.
Valvoline makes a 4-stroke motorcycle oil. Castrol has always been a choice.
I don't think there is the need for an oil additive if you use the right oil for a motorcycle.
Stay away from V-Twin or Harley oils as their motors are non-unit design, i.e.: the motor is separate from the transmission and the clutch.
It is more important to use a gasoline additive to stabilize the crappy fuel we have and provide some lead for the valve seats.