The Blues are now 18 points behind league leaders Arsenal and, crucially, seven away from the Champions League qualification spots.
Graham Potter’s side will next face champions Man City at Stamford Bridge on Thursday evening before travelling to the Etihad Stadium to face them in the FA Cup on Sunday.
Zakaria, who has been one of Chelsea’s better performers of late, urged his side to find answers to their problems as they approach the second half of the campaign.
Speaking after the 1-1 draw with Nottingham Forest, Zakaria told reporters: “We drew and it is not a good result for us but we have to work and be ready for Manchester City.
“It’s hard to say [what’s going wrong] but we have to play better. We didn’t play well [against Forest]. It’s difficult to take the three points here if you don’t play well.
“We just have to work as a team and it will get better. It’s difficult to say exactly why it is not working.
“Chelsea is a big team. We all know that. Yes, it is a difficult time for us but it will improve in the future, for sure.”
The Switzerland international has lined up just four times for Chelsea since joining on transfer deadline day in an initial loan deal from Borussia Monchengladbach that could turn into a permanent £27million move.
Three of those appearances have come in Chelsea’s last four matches with Zakaria’s displays forcing his selection.
Having started against Man City already in the Carabao Cup, he hopes to keep his place amid competition from Jorginho, Mateo Kovacic and Conor Gallagher for a central role.
“I will prepare for it like the other games,” he added. “Every team is good in the Premier League so you have to prepare. I will be ready like always.
“We’re looking forward to playing in a top football match. Against City, it is always really, really difficult so we will have to play well and score all our chances.
“We will have to do a big game, if we don’t do a big game against Manchester City then it is hard to win.”