Based on what we've seen of her so far Tabitha is shaping up to be one of the most lethal enforcers we've seen in the show thus far... So it's obvious this rumble had to happen at some point.

Skills: Tabitha has shown proficiency with various melee weapons, h2h, and firearms, and it's implied she knows all too well the principles/techniques of mental conditioning through torture. Victor Zsasz is very similar in that we've seen him to be a rather quick and precise killer who apparently knows how to break and mentally reprogram a person to do what he wants.

Round 1. Close Quarters Combat including melee weapons. Tabitha has been shown to be use a whip most effectively, as well as knives and sharp stiletto heels, and of course h2h, Victor, given his knack for torture, I have to assume he knows how to wield various implements that might otherwise be considered deadly implements.
So who wins this round?

Round 2. Shoot-Out, No Sniping. While Tabitha has shown some skill with a Sniper Rifle (having executed one man, and wounding another on two different occasions.) We can reasonably assume shes a good shot. However we don't know how she handles shooting while under fire. Victor on the other hand seems very comfortable while shooting under pressure, once having waltz right into gun fire against a squad of heavily armored Gotham Strike Force officers, and only being wounded himself. Who takes this round?