I have to take daily Zyrtec (cetirizine) (10mg). Liver-wise, is it safe to have one glass of wine on a day when I take this med? Or do I need to avoid any alcohol?

No problem. although it may potentially have an additive effect to the drowsiness induced by alcohol . Make sure you don't drive after the combination on the first occasion just to make sure. If no problem, you may even try 2 glasses of wine and do the same observation but no more.