Z-moves and weather at the end of turn

[pyrromanis 70]

So i was battling wild pokemon while raining in the Opal Ward with my Serperior that holds the Normalium-Z and knows the move Hidden Power. So when I ko a pokemon with any normal attack the battle ends normally and get the exp right as the pokemon faints. But if i ko a pokemon with the Z-move (Breakneck Blitz in this case) it shows the rain animation when the pokemon faints and then I get the exp as usual. Maybe there something wrong with the order of weather when use a Z-move (and maybe other effects too?)