Im assuming this was done on turntables and if it isn’t turntables then they’ve used some big time editing!!haha..
but seriously...i personally think its turntables.
When i do a vocal track and want to do something like that i usually just mute the bits i want cut out. Like low the volume complete.

Im tired there's probably a better way to explain this, sorry
I Like Deathcore, Deal With It!
dunno how they'd do it live, they probably wouldnt, but its just done by automation. meaning, they make the sound go up, then down, then up etc nice and fast. BUT. in that song they dont mute it. it sounds like theyve just taken out the mid and highs. but yeah same basics. just making an eq do something.
The easy way is to use samplers.
You load vocal sample up and then you can control pitch, lenght and all.