Braintree came out flying after the break, nearly scoring within the opening 10 seconds of the half, however Izquierdo was alert and made a point blank save to deny Trialist C’s volley.
He was called into action again to turn another shot behind from Innih Effiong, as the hosts looked as though they'd found a foothold in the game.
This wasn’t the case, as Killian Phillips added a fourth for Palace to quell Braintree’s momentum in the second-half. Malachi Boateng picked out Jesse Derry with a sweeping ball, and the winger slipped in Phillips who took it round the ‘keeper for an easy finish.
After Phillips’ goal came six additional changes to compliment the four at half-time, giving way to an entirely new outfield compared to the one that started the game.
Umolu stung the palms of Knightbridge in the Braintree goal with a quarter of an hour remaining in search of a fifth, which eventually came from Jesse Derry’s stunning 20-yard strike with four minutes remaining.
The winger netted his first ever goal for the U21s and that rounded off a stunning win for Powell’s side ahead of their next pre-season game against QPR’s Development Squad on Saturday.
Braintree: Knightbridge (GK), Trialist A, Langston, Annesley, Trialist B, Vennings, Blackwell, Miranda, Effiong, Cooper, Trialist C.
Subs: Clampin, Roberts, Barnes, Reggie Lamb, Trialist D
Palace: Izquierdo (GK), Nascimento (Grante, 62), Rodney (Browne, 62), Farquhar (Akinwale, 62), Jemide (Trialist, HT), Umeh (Marjoram, HT), Boateng (Mustapha, 62), Phillips (Reid, 62), Mathurin (Derry, HT), Ola-Adebomi (Umolu, 62), Devenny (Marsh, HT).
Sub not used: Eastwood (GK).