'Korang' is a short form of 'kau orang' in Malay language. 'Kau' means you and 'orang' means people or person. But when these words are combined, it will become 'you guys' or just 'guys'. It's an informal word.
1. Korang pergi mana? (Translation: where are you guys going?/where did you guys go?)
2. Korang, aku nak pergi tandas. (Translation: guys, I want to go to the toilet).
'Diorang' or 'dorang' is a short form of 'dia orang' in Malay language. 'Dia' means him/her and 'orang' means people or person. But when these words are combined, it will become 'they' or 'them'. It's an informal word. The formal one is 'mereka'.
1. Diorang cantik! (Translation: they're pretty!)
2. Aku nak berjaya macam diorang. (Translation: I want to be successful like them).