Parker's strike settled a roller-coaster clash at Upton Park on Saturday and allowed the Hammers to take a giant stride towards Premier League safety.
West Ham's goal difference means they cannot realistically be overtaken by Hull and if Burnley fail to win at Liverpool on Sunday then Zola's men are safe.
"It was a great finish and not an easy shot because he did not have an angle, but he hit it perfectly and it was a great goal and great result," said Zola.
"I cannot celebrate yet. We want to stay focused and want to finish this championship with some more points."
Only four weeks ago, Zola left Upton Park considering his future in the job after West Ham had lost to Stoke, their sixth straight defeat.
Zola said he was persuaded not to leave by the fighting spirit of his players and he believes that togetherness is key to their turnaround.
"It was never my intention to leave this place in the situation we were in. Everybody was down and in those moments, feeling the players behind me and their fighting spirit helped," he said.
"I understand the fans were nervous like us and the way we started the game did not help, but they have been behind us and while we have not given them much satisfaction they have always been behind us and I'm grateful for that.
"[The players' reaction to the goal] was very gratifying. It shows that despite all the problems, there has been a compactness between players and staff.
"There has been a lot of stick but we have been together and that is the result, that was the meaning of the celebration."
Wigan took an early lead through a Jonathan Spector own goal and would have doubled it soon after had Robert Green not pulled off a brilliant save to tip James McCarthy's strike onto the bar.
It was a key moment as West Ham raced into the lead with goals from Ilan and Radoslav Kovac. Hugo Rodallega drew Wigan level again before Parker stepped up to seal the victory.
"The save was the key moment. Going two down against Wigan would have been tough, but the reaction was amazing and we never let ourselves down," said Zola.
Wigan manager Roberto Martinez was disappointed not to have left West Ham with at least a point but the club's top-flight status can also be secured if Burnley fail to beat Liverpool.
Martinez vowed there would be no let-up from Wigan, who could have a say in the title race when they face Chelsea on the last day of the season.
"I think it is frustrating not to get something from the game. We deserved something from it," he said.
"Winning would have been difficult because West Ham were in a positive frame of mind but to have more chances and more corners is where you get frustrated.
"If we had that two-goal cushion it could have been different. We allowed West Ham to score three goals out of very little. But take nothing away from Scott Parker's goal - that was a real touch of magic.
"Mathematically we're not safe yet. We have a young squad and I was proud of them. It was a hard place to come and it shows how far we've come.
"I don't like to look back, not until the end of the season. We have to go to Chelsea and have a say in the title race.
"To finish the season there, we can show the lessons we've learnt. It will go to the final whistle."