The Canadian winger scored the first, won a penalty for the second and delivered the corner kick that provided Raith's third as he terrorised his former club throughout an eventful performance to make amends for his red card at Celtic Park in midweek.
He was denied the man of the match award - club captain Kyle Benedictus a deserving recipient after scoring a rare double - but there is no doubting Zanatta is Rovers' man of the season so far.
His opener was his sixth strike for the Kirkcaldy side in 13 appearances since moving from division rivals Ayr United during the summer as the former Hearts prospect reignites his career under John McGlynn.
The 24-year-old was unplayable in attack but constantly cajoled by his manager to stick to his defensive tasks. Sometimes looked upon as a luxury player, McGlynn revealed how he is getting the best out of him.
"How you can describe Dario is if you were in horse racing, you would need to keep the whip out,” he said. “You need to keep at him. You can’t give him free rein.
"Dario is horizontal. He is laid back as anything. Nothing bothers Dario, but we’ve got him in a great place and he’s putting up fantastic numbers.”
Zanatta struck from 18 yards on 22 minutes then won his side a penalty on 64 minutes when his flick struck a Thistle hand in the box before centre-back Benedictus drilled home the spot kick.
The same player made it 3-0 with 12 minutes left, side-footing home after Thistle failed to clear Zanatta's corner.
Partick contributed to an entertaining match and pulled back two late goals through Brian Graham and Zak Rudden having had two earlier penalty appeals turned down when Graham’s shot struck Benedictus’ arm and Ross Matthews bundled over Ross Docherty.
Jags boss Ian McCall said: “The first I think is a penalty, I’ve seen it. The second one I don’t even need to see. It’s the clearest penalty you’ll ever see.
"One or two things didn’t go our way and we just have to suck it up and get on with it.”