The on-loan Juventus star has yet to register a goal for the Hammers since joining in August - a run now spanning six games in all competitions.
Despite failing to find the net so far, Bilic was more than impressed by the Italy international's display at Selhurst Park and believes that it is just a matter of time before he finds his feet in the English top flight.
"Zaza was different class on Saturday," he told the club's official website. "I told him after the game 'This is the Zaza I know from Sassuolo and from Juventus and the goals will come'. Goals are really important for strikers, but they will come.
"I told him after the game straight away 'Zaza, you won today. Tonight you won more balls in the air against two good centre-halves in [Damien] Delaney and [James] Tomkins than you won in the four or five games you played before'. Without him, we wouldn't have won, it's as simple as that."
West Ham will reportedly have to fork out £20m to sign Zaza on a permanent basis should he make another nine league appearances this term.