Oxidization is tough to deal with , you need to remove the dead paint and refeed the oils etc that are missing. Some will never come up.
Doing this by hand is tough ... don't go heavier as your cutting away more than needed .. your going to need more of a chemical cleaner wax like Meguiars ColorX and then it might be some work.
The reason the Zanio AIO is doing that is the cleaners in it are picking up some remaining dead paint and contaminating itself. The AIO is meant for clear coat not single stage.
In the last 2 weeks I have done 3 single stage cars .. one a 56 Pontiac barn find and badly oxidized. It took a PC and 4 medium cut pads and a compound to do the hood/roof/ trunk alone.
In the end I found the best look was with Meguiars #26 wax as its a heavy paste and fed the paint some.