Zero fee for the particular pair? No thanks, it is an attempt to pump the project I guess and they got paid for it already.
It is better to find the obvious ones like native tokens get discounts on fee or just pick the ones among the cheapest and also got the trading volume to handle the trades.
I would always appreciate when I trade, I pay my fees and do my transactions smoothly rather than look for zero fees trading and get stuck along the way because I believe volatility has a role to play here and am sure no exchange want to run out of business soon.
There are new regulations particularly in Europe that force the evolution of these zero fees models, but there always has to be a catch behind so no lose is incurred because some try to take advantage of the zero fees service.