Quote Originally Posted by Aotrs Commander View Post

Spoiler: s9e4

I was windering why the hell Zephr was suddenly a guard (but watching Rainbow squirm and Rarity's expression meant I didn't worry too much), but it was All Part Of The Plan by the true mastermind - Spike!

Spoiler: S9E4
I wouldn't put it past Luna to have recruited Zephyr and stationed him there so that they could get through.