Reigning champions Inter came through what was supposed to be a tough test at the Stadio Olimpico with flying colours and are three points off the Scudetto pace with a game in hand.
Substitute Zaniolo decided a hard-fought encounter in Sardinia by stroking home Raoul Bellanova's cut-back in the 66th minute and moving Atalanta five points clear.
Edoardo Bove has had a defibrillator fitted after the Fiorentina midfielder's on-pitch cardiac arrest earlier this month, according to widespread Italian media reports on Tuesday.
Fiorentina earlier remained on Napoli's heels after their 1-0 home win over Cagliari in their first league match since midfielder Edoardo Bove's sudden collapse last weekend.
Edoardo Bove is conscious and alert in hospital after his sudden collapse which caused Fiorentina's match with Inter Milan to be called off, the Serie A club said on Monday.
Fiorentina's Serie A match with Inter Milan was stopped on Sunday after midfielder Edoardo Bove suddenly collapsed to the ground.
"It's too early to talk about the title. All we can do is look out for how we develop as a team, work to improve and win every match we play. But now is not the moment to talk about the title," said Lukaku.
Juventus remain the only unbeaten side in Serie A but their seventh draw of the season means they remain sixth in the standings and are now three points behind leaders Inter Milan. Milan stay seventh, six points behind Juve, though they have played one game fewer.
Simone Inzaghi's side are provisionally ahead of Napoli after netting all five of their goals in the opening 45 minutes at the Stadio Bentegodi through a Marcus Thuram brace and further strikes from Joaquin Correa, Stefan de Vrij and Yann Bisseck.
Napoli coach Antonio Conte criticised the Video Assistant Referee (VAR) for not intervening to reverse a penalty that Inter Milan's Hakan Calhanoglu eventually missed in their 1-1 draw on Sunday.
The victory, provisionally, leaves Juventus level on points with champions Inter Milan in second and one behind league leaders Napoli.
Inter are now in second place in the table with 24 points, one behind leaders Napoli, while Venezia are 18th.
Forward Ademola Lookman scored twice inside the first half to help Atalanta to an emphatic 3-0 win at Serie A leaders Napoli on Sunday as the visitors moved second in the standings.
The record 36-time champions trail second-placed Inter Milan on goal difference after Maduka Okoye's own goal and Nicola Savona's effort.
Antonio Conte's resurgent side wrapped the match up inside the first half, courtesy of an early Romelu Lukaku goal and a sensational strike by Khvicha Kvaratskhelia.
Manager Thiago Motta acknowledged that Juventus are not in the Serie A title race just yet and emphasised the importance of maintaining focus on their growth after they secured a dramatic 4-4 draw with champions Inter Milan thanks to two late goals on Sunday.
Argentina striker Martinez lashed home his fourth goal of the season in all competitions on the hour mark after a poor clearance from Zeki Celik to give Inter a hard-fought win at the Stadio Olimpico in Rome.
Defender Gabbia rose highest to thump home Tijjani Reijnders' free-kick in the 89th minute and give Milan a Serie A win which pulls them out of a miserable early season slump.
Juventus were held to a 0-0 Serie A draw at Empoli on Saturday as Thiago Motta's side dropped more points after their goalless home stalemate against AS Roma before the international break.
