How to deal with GenZ digital marketers (juniors) in agency, who thinks they know everything and not corporating with experienced digital marketing managers

My friend raised this question today that he joined a startup agency, he has mixed both agency and client side marketing experience, he leading a team of 7 digital marketers, all GenZ, when he tries to tell something with his experience, they like we know everything in digital despite they are only 1-3 years experienced,

not accepting any feedbacks, with AI, they think they are masters of Digital marketing

and he is struggling to lead them, (he is a first time manager managing team of 7), previously managed only 2, but well expeirenced in marketing , consumer behaviour, client relationship along with digital mastery