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 was struck by a relapse of the disease from which he suffered for a portion of last season, and is currently in New York City receiving treatment.
"He's fine. He's recovering and he's in high spirits," he 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 2-1 win over Granada on Saturday as they prepare to face AC Milan in Europe on Wednesday.
"We know how important the league and the Champions League both are," the 51-year-old continued. "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."
When queried whether David Villa and Xavi would be fit for the showdown at San Siro, the 51-year-old replied: "That's up to the medical staff, but we hope so."