Contradiction with Matthew 21:1
This verse agrees with Mark 11:1 about the approach to Jerusalem, thus any contradiction would have to involve differing details such as the subsequent instructions or events.
Matthew 21:1: And when they drew nigh unto Jerusalem, and were come to Bethphage, unto the mount of Olives, then sent Jesus two disciples,
Contradiction with Luke 19:29
Similar to Matthew 21:1, this verse parallels Mark 11:1 regarding the location, so any contradiction would relate to specifics beyond the approach to Jerusalem.
Luke 19:29: And it came to pass, when he was come nigh to Bethphage and Bethany, at the mount called [the mount] of Olives, he sent two of his disciples,
Contradiction with John 12:12
While this verse describes a surrounding event, any contradiction with Mark 11:1 would depend on timeline sequences or details not explicitly stated in Mark.
John 12:12: On the next day much people that were come to the feast, when they heard that Jesus was coming to Jerusalem,