According to the MSDS for Zippo Lighter Fluid, it is 70% "Light Hydrotreated Distillate" and 30% "Hydrotreated Light Naphtha".
That makes it very close to the same composition as many fuel additives.
To break it down to the basics, it is light machine oil (3-In-One oil, sewing machine oil, etc.) and Naphtha. Some fuel additives may add in a little Benzene (which can cause cancer, they say).
Looking at Material Safety Data Sheets is a favorite way to pass the time for me. It can be very educational!
Ether starting fluid is, of course, just exactly that: Ether!
Actually, according to one MSDS, it is:
40-50% Diethyl ether
40-50% Heptane, severely hydrotreated
Less than 1% mineral oil
4-7% carbon Dioxide