A three-horse race for the Spanish championship has been whittled down to two as Madrid and Barca both won at home against Valencia and Espanyol respectively, but Atletico Madrid lost.
It leaves Los Merengues still one point adrift of Barca ahead of their trip to Deportivo La Coruna, while Luis Enrique's men must face an already-safe Granada outfit.
Although Barca are in the driving seat, Zidane insists he has not given up hope of lifting the trophy in one of the tightest title races in years.
"I'm always positive," he said in quotes published on Real Madrid's website after their 3-2 win over Valencia.
"Now we are second and we have one game left to play, anything can happen. In football you never know what is going to happen. We have to give everything and keep going until the end and we will see what happens.
"We have a match which will not be easy. I never saw an end to the season as tight as this when I was a player. We will see what happens right up until the end, until the very last minute."
Cristiano Ronaldo scored twice and Karim Benzema also found the net against Los Che, but the visitors pulled two goals back in the second period and looked dangerous until Rodrigo, scorer of Valencia's first goal, was dismissed late on.
There was no Luka Modric or Gareth Bale in Zidane's starting line-up - both players are injured - while the likes of goalkeeper Kiko Casilla and defender Raphael Varane came in too after the UEFA Champions League semi-final win over Manchester City.
Zidane has a Milan date with Atleti in the Champions League final to consider, yet he vowed to name his strongest possible line-up against Deportivo.
"There will definitely be rotation, but only with the focus on that game," he added.
"We have 15 days afterwards to prepare for the final. There is time to think about Milan. We are all going to La Coruna because anything can happen until the end and until the final minute."
Madrid were fortunate that Benzema's goal on the stroke of half-time that made it 2-0 was allowed to stand as he was clearly offside when he fired in a first attempt from Ronaldo's cross.
Valencia felt aggrieved then and they were incensed late on too when Rodrigo was dismissed for something he said to the referee.
"The referees were not right; I cannot understand how an offside of a metre-and-a-half was missed," boss Pako Ayestaran said on Los Che's website.
"A draw at least would have been just. Now I am concentrating on the next game. The referee has said that everyone can make mistakes, they are aware that they have made a mistake. Rodrigo has said things that in 80 per cent of situations would have led to nothing."