Al Jazira are appearing at the tournament as champions of the host nation the United Arab Emirates, and reached the last four by edging out Auckland City of New Zealand 1-0 and then defeating the Asian champions Urawa Red Diamonds by the same score-line at the weekend.
"It is not going to be easy for us. If we think that we are wrong," said Zidane at a press conference on Tuesday.
Real are hoping to successfully defend the Club World Cup trophy they won in Japan 12 months ago -- when Cristiano Ronaldo's hat-trick in the final helped see off Kashima Antlers -- and win a club record fifth title in the same calendar year.
But Zidane warned that, for Al Jazira, who are coached by the former Barcelona assistant boss Henk ten Cate, "this is their game of the year and that is why we need to be prepared".
Of the prospect of winning a fifth trophy this year, he added: "I don't think (this would be the club's best year) because Real Madrid is a big club, but it motivates me and all the players.
"We want to defend the title we won last year and that is why we came here."
Zidane's squad travelled fresh from a 5-0 win against Sevilla in La Liga at the weekend and the coach indicated that both Gareth Bale and Raphael Varane could be involved in the game, which kicks off at 9pm local time (1700 GMT) at the Zayed Sports City Stadium.
"On Monday and today (Tuesday) they trained well, without problems, and took part in the whole session," Zidane added of the duo.
If Madrid win Wednesday's game, they will face Gremio in the final on Saturday after the Brazilians beat Pachuca of Mexico 1-0 after extra time in Tuesday's first semi-final in Al Ain.
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