The Barcelona sporting director says the coach is in high spirits and has put on weight since going to New York City to receive treatment for cancer.
The 44-year-old took the reins at Camp Nou outfit in the summer, but he was struck by a relapse of the disease in his throat from which he suffered for a portion of last season, and he is currently in New York City receiving treatment.
"He's fine. He's recovering and he's in high spirits," Zubizarreta told reporters. "He is grateful for all the support people are giving him. He has put weight back on and is watching football every day."
Zubizarreta went on to voice his delight with the club's 2-1 win over Granada on Saturday as it prepares to face AC Milan in the UEFA Champions League round of 16 on Wednesday.
"We know how important the league and the Champions League both are," Zubizarreta said "Teams used to playing in a number of competitions are able to concentrate in every game.
"It was not easy to win against Granada, however. They are an intense team who are very quick on the break. We played well in the first-half but we couldn't score. In the second half we were more clinical."
David Villa (kidney stones) and Xavi (hamstring) both missed Saturday's encounter, and when asked whether the two Spanish internationals would be fit for the first-leg showdown at the San Siro, Zubizarreta said, "That's up to the medical staff, but we hope so."