Mine are a bit like this, but slightly younger than yours.
I'm not sure there are easy answers, accept that some squabbling is natural and healthy, they're gaining skills in managing conflict, asserting themselves, seeing others' viewpoint etc.
Model the behaviour you want them to show, try not to step in with shouting when they are shouting. Talk them through calmly and say 'X, Y is angry because you did Z. Y, X did that because you did another thing'. Pretty much bore the shit out of them talking through the situation when they argue, but don't make it escalate into a slanging match.
Praise them when they're being nice to each other, playing nicely etc.
Set out where the line is and have consequences for stepping over it. Find a consequence they do care about. I always tell mine they have to watch the news on TV!
See if you can carve out time to pay them more attention, 121 etc - easier said than done, I know! Try to pay them full attention when you're together, not looking at phone etc.
Anticipate times they are most likely to fight and see if you can do something to change it - eg maybe they're hungry or tired, can you give them a snack when you come in.
Encourage them to find ways to calm down, maybe by going off for quiet time, reading a book etc - being in different rooms if they're winding each other up.
That 'how to talk to kids so they listen and listen so they talk' book is often touted on here, I've got it on my shelf but haven't got round to reading it!
Dunno if that helps, I'm struggling with the same things myself!