Can Rex L, zKylo, B2, Chaze beat Zaul team?

Easily. Rex TM lead and multiple cleansers beats Sith pretty easy. Honestly I know zDM is a popular leader, but probably the best D-slot involves Chaze in various forms. Many teams - including zDM comps - can't handle Chaze very well in multi-cleanse teams. I think the zDM heavy mix we see on leaderboards is more to do with the Sith being commonly owned as compared to Chaze less people have them to put in D slots.