Revealing mistake: In the opening scene when Zorro (Anthony Hopkins) is freeing the peasants and jumps down from the top of the mission to the small balcony, you can see that the bricks where he lands actually either are made of or mounted on some type of rubber as they give way and bounce back under his feet when he lands there. (00:07:55)
Continuity mistake: In the same part, he is now standing on top of the wall. Zorro takes out his whip and wraps it around the tree limb and swings over to the other part of the wall. When he lands on the wall, he takes off running, letting go of the whip. When the camera returns to him running on the wall, he has a new whip, all rolled up in his hand. (00:08:05)
Continuity mistake: Near the beginning of the movie, after the big fight scene, Zorro rides up the steps on his horse and behind him you can see that the sun is setting, which means it should be early evening. But whenever it shows the boys, the light on them and the landscape makes it appear to be mid-day. (00:09:25)
Continuity mistake: When Alejandro and Diego fight in the cantina, Alejandro knocks over stalks of corn rolled up in a bundle into the doorway. In the next shot, the corn stalks are standing again. (00:35:30)
Continuity mistake: When in the cantina, at the time the corn stalks disappear, Zorro knocks the sword out of Alejandro's hand. The sword seems to fly back behind him. In the next shot, Zorro catches the sword because it is now falling straight from the sky. (00:35:40)
Continuity mistake: When Antonio Banderas is finally proficient at swordsmanship, he knocks Anthony Hopkins' sword out of his hand and catches it. He then laughs and throws it back pointing downwards, but when Anthony Hopkins catches it, it's pointing upwards. (00:41:00)
Other mistake: Later in the movie, when Alejandro is getting his horse, he lights the cannon. Then he throws the torch down and it lights the powder. He picks up the keg of powder and runs out the door. As he is running, you can see that there is already a line of powder on the ground that he is running over. (00:51:35)
Continuity mistake: Later in the movie, when Alejandro is now Zorro and in the house confronting Captain Love by drooping in behind him. Watch the tip of the sword as it moves to a different location on the Captain's uniform. (01:32:55)
Revealing mistake: In the scene where Captain Love and Antonio Banderas (as Zorro) meet in the hallway of the hacienda, two guards rush down the hallway and drop their rifles and swords. Zorro asks them to bend over and then proceed to kick/nudge them out the window. If you watch carefully, you'll notice that the guard on the right (furthest from Zorro) reacts to the kick too early. (01:33:30)
Revealing mistake: In the scene where the Dons are looking at the map of California, Zorro runs in and cuts it down, over all of the men. You can clearly see that strings are pulling it over the men. (01:36:00)
Continuity mistake: During the Alejandro/Elena fencing sequence, after he kisses her the first time, her left sleeve is down. The shots before and after have it covered. He slices the fabric off in the next shot. Her right sleeve also came down for no reason. (01:38:15)
Audio problem: During the scene when Anthony Hopkins is in a dark corner and starts talking to Don Rafael, his lips move at different times than his speech heard on the screen. (01:47:25)
Other mistake: In the ending shots, when the hoist is bringing up the last of the gold to the wagon, why is the wagon covered up if they still have gold to put in it? (01:52:40)
Revealing mistake: In the ending shots, when Alejandro and Captain Love are fighting, when Captain Love falls down the hill, Alejandro grabs a shovel and slides down the hill. If you look at the shovel, you will see the strap that holds his feet to it. (01:59:00)
Revealing mistake: When Elena is rescuing the people near the end and shoots the lock off a door, you can see the lock fall open before the squibs go off, in other words it breaks first then gets "hit" by the shot. (01:59:15)
Continuity mistake: When Alejandro and Captain Love are fighting on the gold lift, Alejandro punches the sword out of Captain Love's hand. He grabs it and stabs it through him. When it shows the top view of the sword stuck in Captain Love, hit the pause button. Look at the sword blade going through Captain Love's stomach.Then look at the other end of the blade going out of his back. They are at different places in him. (02:03:00)
Factual error: During the scene towards the end of the film where Alejandro is chasing Captain Love in the shack with the furnace at the mine, we see a pressure gauge just before the furnace explodes. The unit of measurement on the pressure gauge is shown as kg/cm2. Metric measures were not used in Mexico until eleven years after the film was set, and as California was a part of Mexico at the time, metric measurements would not have been used there.
Other mistake: Near the end of the film there is a stand-off, if you look in the sky an aeroplane flies by.
Factual error: The movie takes place 20 years after 1821 which would be in the year 1841. There is a line that says that Santa Anna is at war with the United States. But the Mexican war did not break out until 1846. Santa Anna was not at war with the U.S. in 1841.
Audio problem: At the very beginning where the two young boys cut the eye holes, the sound of cloth ripping is not synchronized with the knife cutting it.
Answer: He recognized that Bernardo was really Diego de la Vega and he realized that the young Zorro he had seen earlier could not have been Don Diego. He then deduced that the new Zorro looked similar to Don Alejandro (and was probably warned by Captain Love that Don Alejandro was hiding someting) and made the decision.