Genie Twilight: I'll still inform everything about Zathir to not just Human me, but also to Sunset so she could pass that along to the Pony me of that universe. As Zathir would also have to have permission to enter the castle to even get to the mirror. That'd be the first line of defense against him for Human me, but the transformative mirror would work as a wonderful 2nd line of defense just in how surprised Zathir would be when he ends up flailing around, not being able to walk normally. And probably getting some weird stares from high schoolers in the meantime.