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.
Argentina forward Martinez glanced home the decisive goal in the 14th minute of an action-packed contest in Florence in which Nicolas Gonzalez wasted a late penalty for the hosts, who had Inter on the back foot for much of the game.
Nigeria striker Victor Osimhen will leave Napoli this summer and join "either Real Madrid, Paris Saint-Germain or an English club", the Italian club's president and owner Aurelio De Laurentiis said on Friday.
Sardinia was mourning the loss of a sporting deity on Monday after the death of former Italy striker Luigi "Gigi" Riva, who did more than anyone else to put the Italian island on the footballing map.
Napoli put aside their recent troubles on Thursday by reaching the Italian Super Cup final with a convincing 3-0 win over Fiorentina in Riyadh.
A stunning first-half brace by striker Dusan Vlahovic helped Juventus to a 3-0 win over Sassuolo in Serie A on Tuesday as Massimiliano Allegri's side extended their unbeaten league run to 15 games in front of a sold-out home crowd.
The 37-year-old Giroud was in the perfect position to head in their second goal before his brilliant back-heel flick set up Theo Hernandez for the third.
Doubles from Hakan Calhanoglu and Lautaro Martinez and a late strike from Marcus Thuram extended Inter's advantage on Juventus, who host Sassuolo on Tuesday night.
Napoli striker Victor Osimhen has replied angrily to suggestions that he would leave the Serie A side for Saudi Arabia at the end of this season from agent Mamuka Jugeli, who represents club team mate Khvicha Kvaratskhelia.
Fiorentina beat Serie A rivals Bologna 5-4 on penalties to advance to the Coppa Italia semi-finals on Tuesday after their last-eight clash finished goalless after extra time.
AC Milan consolidated their place in Serie A's Champions League positions on Sunday with a straightforward 3-0 win over lowly Empoli.
