Midfielder Ambrose, last season's 20-goal top scorer, has yet to recover from a leg injury and rookie striker Zaha serves the final game of his three-match ban.
But Edgar Davids could return at Selhurst Park after missing Saturday's defeat at Reading due to personal reasons and Tottenham loanee Jon Obika hopes to shake off a calf strain.
Recent loan signings James Vaughan and Anthony Gardner should make their home debuts while Pablo Counago is pushing for a recall to the starting line-up.
Defenders David Wright (calf) and Lee Hills and winger Sean Scannell (both knee) are still on the sidelines.
The Championship match kicks off at 8pm.
