Diaz was involved in both opening two goals as he provided the assists for Safiq Rahim and Luciano Figueroa to score in either half.
Diaz then netted a brace before Figueroa scored again late in added time.
Johor got off to a perfect start when they scored after two minutes as Safiq burst into the penalty area from Diaz's square pass to round goalkeeper Vanlal Hruai and score.
In the 19th minute Figueroa nearly doubled the lead but his header from a cross was well saved by Hruai.
Despite dominating the hosts could not score a second goal in the first-half and went in at the half-time break leading 1-0.
Figueroa scored two minutes after the restart as Diaz dribbled past two defenders and passed the ball to his compatriot who scored from close.
Ayeyawady had virtually no chances in the second half and the one chance they had was easily dealt with when Aye Ko Ko Maung headed a free-kick straight at the Johor goalkeeper.
In the 62nd minute Diaz scored the third goal when he skilfully wrong-footed an Ayeyawady defender before firing low into the net to make the score 3-0.
Diaz made it four on 74 minutes with a header from a Safiq corner.
Figueora completed the defeat in injury time when he headed home another Safiq corner to make the score 5-0.