During my time gambling, I was quite unfamiliar with zero edge. I thought they only existed in real-world gambling or if you went to a specific casino and played live. Online casinos never explicitly state that they are zero edge casinos. Even if this were the case at a casino, how would they pay their employees or generate profits for their own company? Perhaps this zero edge only applies for a limited time, like most events.
Actually, there are a few casinos which use the "zero edge" feature as some kind of advertisement for them in order to attract gamblers in this very competitive market, you see?
They still manage to make money because those zero edge conditions are rather limited to a very few games and during a short period of time or with a very limited size of wager.
There is always some way for the casino to monetize or capitalize their zero edge games, otherwise they would lose money because of it, and we all now casinos and bookies are not in this business to lose money.
The lastest casino I have seen to support zero edge games (allegedly) is Duel. Though, be adviced, they have lately partaken in very wacky and edgy advertisement in order to get people's attention.