A lot of hobbyists, myself included, found Rail-Zip to be a dirt collector requiring repeat applications more frequently to maintain electrical conductivity.
Oil-based cleaners also tend to reduce traction.
I used it in N scale decades ago on Atlas nickel silver track. I discontinued using it after I saw the amount of dirt that was collecting on the rail heads and freight car wheels, which translated into need for more frequent cleanings.
Unless a contact point is corroded, I have found that a good solvent is better for maintaining electrical conductivity. I use denatured alcohol and a cloth diaper to clean the rails.
However, the contact points, specifically the rail joiners, on FasTrack, do seem to benefit from a contact cleaner aimed at restoring electrical conductivity. I use Caig deoxIT DN5, applying it only on the joiners with a needle applicator. You might try doing the same with Rail-Zip.
