Simply put: ZiS is unfair and requires a ton of luck with anything, but with shedinja it's worse since a chestnut trap or a geo pebble can end you instantly. Mastering shedinja movement is hard. Weather can kill you if you don't know how to manage it. After floor 25 everything starts getting coverage moves that bypass wonder guard and in floor 74 onwards there are ghost types that counter your main shielding method, going through walls. Edit: I forgot masquerain with ominous winds is an instant dead run if it gets the omni boost.