While Cardiff, who the Hornets face this weekend, have a seven-point lead at the top and look destined to secure the Championship title, the identity of the team who will finish second - and also go up automatically - is far from decided.
Hull currently occupy that spot yet their 1-0 defeat to Zola's men on Tuesday night has given them just a one-point advantage with Crystal Palace also in the mix.
But with the Tigers and Hornets enduring inconsistent form of late and the Eagles crashing to three straight losses, Zola is anticipating plenty of surprises in the final six games.
When asked if the race for second will be determined on the final day, Zola said: "It will certainly be like that.
"It is a season, you can see around us, it is crazy. You can't say `you beat Hull and all the other games are easy'. We've found we've had more problems with small teams than with big ones.
"It will certainly be down to the end but not just for us, it will be difficult for everyone."
While the Italian, an icon of the top flight during his playing days, has managed in the highest domestic division with West Ham, he insists attaining promotion with this Watford squad would be even more special.
"It would be fantastic to achieve it with these guys," he added.
"We work very hard and I'm pleased, proud of that. It would be a great reward for the Watford community if we can achieve that but it's going to be tough, that's for sure."
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