REZ is not as strong as it was before, despite being called a T1 deck it actually has difficulties fighting against backs such as dinos and gladiators, it's also not as fast as the OTK decks in beatdown hazy or Saffira CA. Both dinos and gladiators are also cheaper to build overall, you may wish to look into those if you want a competitive deck.
@Anthony I been playing REZD since June. REZD had been in the top for awhile but it's not as dominant like back in its prime. it goes up and down in the tier list and like the other ones have said currently is not doing so good and thats true but you can still hit KOG with it and Max on the KC CUP but it wont be easy. regardless investing your gems for 3 Gozuki is a safe bet. its a zomie staple
REZD Bonz is still better than GB I reckon. I struggled a lot with my GB deck that got KOG in under 50 wins last season, especially vs the hazy 16 monster spam. REZD took a while to optimise (without Gozuki no 3) but it's more consistent if you include Brachios too.