Ndidi was sent off after receiving a second yellow card for diving.
Mahrez was also on from start to finish in the frustrating tie while Nigeria's Kelechi Iheanacho returned to the subsitutes' bench - for the 13th time since his summer move from Manchester City - but never made it out to the pitch. Ahmed Musa was left out of the matchday squad.
Christian Benteke did not feel he needed to prove anything to his Crystal Palace team-mates as he finally ended his goal drought and atoned for last week's penalty misery.
Muhammad Wilkerson won't travel for Jets at Saints
Updating an earlier report, Jets DE Muhammad Wilkerson was suspended for showing up late to a team meeting on Friday. Before last season, Wilkerson signed a five-year, $86 million extension, a contract that is looking worse every day.
The win lifted Palace to 14th on 17 points, while Leicester are eighth on 26 points in the league table.
As Leicester pushed for a consolation goal in the closing stages, Palace counterattacked with Zaha putting Bakary Sako through, and he finished it off with a fine shot in off the woodwork.
The Belgian striker broke his duck with a trademark header from Andros Townsend's cross on the right to put Palace ahead on 19 minutes.
Crystal Palace allowed an early goal to Watford in the first half and trailed for until the 89th minute.
Weather Authority Thursday Night Forecast : Light Showers to Continue into Friday
Occasional light snow showers will continue for Thursday Night as temperatures remain in the teens for the overnight period. Ending off the work week with temperatures near the seasonal mark with highs in the mid 30s and mostly cloudy skies.
Palace got on the score sheet again this time through Zaha who smashed his effort past Schmeichel after he was played in on goal.
After going behind, Leicester seemed the most likely team to get the second goal, with an appeal for handball on Martin Kelly, causing trouble from a corner in the 33rd minute, and Vardy looking for the bottom corner with a backheel from a Demarai Gray cross.
And 60 seconds later they found themselves down to 10 men, Ndidi picking up his second bookable offence and an unwanted red card on his birthday for a blatant dive inside the penalty area.
Besiktas are reportedly interested in Crystal Palace's out-of-form striker Christian Benteke, as the Turkish club look for alternatives to Cenk Tosun.
Apple iMac Pro will be available for sale starting from Thursday,…
One thing that will make even the ardent Mac users think hard over purchasing this beast, is the price tag on the iMac Pro . As an absolute monster of a machine, the iMac Pro features specifications that are, frankly, a little more than overkill.