The Hornets edged a tight first half but were back to their best after the break, playing some excellent football and cutting through relegation-threatened Blackburn through two-goal Troy Deeney and further strikes from Almen Abdi and Matthew Briggs.
Rovers also had Leon Best sent off in injury time after a coming together with Marco Cassetti.
The win moves Zola's men to within four points of the second-placed Tigers but with Watford travelling to Leicester City on Friday night, the gap could be down to one point before Hull visit Barnsley the following day.
The Hornets head coach said: "I thought it was coming because the performances in the few games have been much in terms of quality, so I was expecting something like this and delighted that it came at the right manner and in the right way.
"What can I say, everything went perfect - a lot of goals, good performance, a good quality of football and a big crowd and a Sardinian day out there. It's been an ideal Saturday afternoon."
Rovers' caretaker boss Gary Bowyer was disappointed with how his side responded to going behind.
"I thought we did well first half. The first goal was always going to be crucial after the backlog of games," he said.
"I'm disappointed in the manner we conceded but you've got to give credit to the lad who took his goals well. We were disappointed with how we reacted, we've not been like that.
"It was probably a big game too many for us but we've got to regroup quickly, we've remained positive and calm throughout and that's exactly the message we've said to them again."
- Sports & Recreation
- Troy Deeney