Guns were never banned at the zoo. The only ones who were banned from carrying guns at the zoo were people who give a damn about obeying the law. People who do not give a damn about obeying the law have always been free to carry guns there.
Do you really feel safer in a public area where the only ones carrying guns are people who do not give a damn about obeying the law? Undoubtedly people who are carrying guns and who do not give a damn about obeying the law feel a lot safer knowing that their potential victims are unarmed.
Awesome, now you can go to the Zoo in Houston and not have to worry about being a statistic.