Such was the Candystripes dominance, they could have easily reached double figures.
Patrick McEleney opened the scoring in the seventh minute with a superb dipping shot from the edge of the area after Gareth McGlynn had found the striker in acres of space.
The home side doubled their lead in the 21st minute when the lively James McClean drilled a low shot into Greg Fleming’s net from 20 yards.
Another McGlynn centre across the edge of the six-yard box in the 44th minute saw Zayed divert the ball home from close range to kill off the game.
Zayed finally netted his second in the 73rd minute when substitute Stephen McLaughlin provided the cross and the big striker powered the ball home with one touch.
And the striker recorded his hat-trick in the 81st minute from the penalty spot after McClean had been upended by Galway skipper Paul Sinnot.
His fourth goal, to make it 6-0, arrived two minutes into added time.
DERRY CITY: Doherty; Molloy, Greacen, S McEleney (McBride 80), Lafferty (McLaughlin 69); McGlynn, Higgins, Deery, McClean; P McEleney, Zayed.
GALWAY: Fleming; S Kelly, Sinnott, Walsh, Keogh; De Silva, Ryan, G Kelly, Moore; Curran, Gilmore.
Referee: D Tomney (Dublin).