It was der Kestle's idea that he would have killed Zeetha - sorrowfully and unwillingly - if she found out he was a Jager, because that would mean Lucrezia in Agatha's head might find out, and that would have eliminated his ability to protect Agatha and the Heterodyne line. der Kestle may have been mistaken.
Also, it's implied Albia knows who he is, but doesn't mind. And, since he's been in Albia's presence and not been fried, that means all the Brits won't give him a second thought. And he IS still nominally on detached duty as Tarvek's servant, and has been for a while; weirdness will be assumed to follow.
I hope long-term Bang can figure out a way to get vengeance without having to kill Zeetha or get killed herself.