Real Madrid secured a dramatic 2-1 last-gasp victory over Las Palmas but Zidane was not satisfied with his team’s performance.
Madrid needed a late winner from Casemiro to emerge victorious after Willian Jose had cancelled out Sergio Ramos' opener in the 87th minute. However, the French manager was adamant that his side had to improve drastically if they had to have any chance of winning the Champions League.
"The most important thing is that we got the full three points, but I am worried about our second-half performance," Zidane said at a news conference.
"I will watch the game back on Monday and analyse things. But I am very worried about the second half. I don't think the win was undeserved, though. We scored from two set-pieces, but that is part of the game.
"Of course, Las Palmas did very well and caused us problems. But what worries me is our own performance.
"We are not thinking about the Champions League. The players are focused on what they have to do. If we want to dream of winning something, we will have to do much better. That is crystal clear. We are going nowhere if we play like this. We cannot play like we did in the second half. I want to watch the game again, but there is no doubt that we cannot play like this."
Zidane unsure of long-term future at Real Madrid
Zinedine Zidane cast doubt on his long-term future at Real Madrid by saying he is unsure if he will be in charge of the club next season.
The former midfielder was named as Rafael Benitez's successor in January when he signed a contract until June 2018.
But when asked what role he would have in the Liga club’s transfer dealings for next season, Zidane said he did not know if he would still be at the Bernabeu.
"I can't know what role I'm going to have if I don't know if I'm going to be here. We'll see what happens at the end of the season,” Zidane was quoted as saying by Spanish newspaper Marca.
The 43-year-old was also asked if Madrid would make another attempt to sign David de Gea after their move for the Manchester United and Spain goalkeeper fell through on the last day of the transfer window last August.
“I’m not planning anything, I don’t even know what’s going to happen tomorrow,” he said.
“All I can tell you is that I’m very happy with our goalkeepers, with Keylor (Navas), Kiko (Casilla) and Ruben (Yanez), and that’s the important thing. We’ll see at the end of the season.”
Zidane is the fifth manager to take charge of Real Madrid since Florentino Perez became club president again in 2009.