My preg girl had yeasty ears too. Glad to know of what solution to use on a preg girl. This girl never has yeasty ears - is it the hormonal changes during pregnancy that change the ear's PH or?
You are fine using Zymox plain, it does not contain any antibiotics or steriods, but contains lactose-based enzymes that kill bacteria and yeast naturally.
It is also pH balanced and does not require any pre-cleaning, in fact it works better without pre-cleaning.
The 50% alcohol/vinegar solution could be very irritating and and painful to an ear with an infection, I would not use that high a concentration of alcohol on already inflammed sensitive ear canals, it's gonna hurt like hell!