Ferreira, who replaced former Real Madrid midfielder Lucas Silva just after the hour mark, struck in the 92nd minute with a glancing header after an Alisson de Freitas corner.
The third goal took the wind out of Mainz' sails as Zentner had his hands full of work. Dani Olmo should have made it 4-1 but Zentner denied him at the hour mark.
Meanwhile all eyes will focus on whether new signing Edouard Mendy goes straight into the Chelsea side or if Frank Lampard keeps faith with Kepa Arrizabalaga after another bad error last weekend.
Midfielder Adil Aouchiche opened the score for the Greens only two minutes into the game after slotting home Yvan Neyou's cross. Left back Yvann Macon extended the lead in the 66th minute but the hosts responded quickly as Moses Simon pulled one back only five minutes later, before Renaud Emond levelled the score for Nice five minutes before the final whistle.
Villarreal kicked off the season with a win and a draw, but strikers Gerard Moreno and former Barca frontman, Paco Alcacer have already shown they can trouble and defense in La Liga.
Guoan suffered criticism after earlier fumbling a 3-0 lead against Qingdao, suffering instead a 3-3 tie in the first leg.
Villarreal came back from a goal down to take their first win of the season with a 2-1 at home to Eibar.
Tosic scored for Taizhou in the injury time.
DALIAN, China, Sept. 21 (Xinhua) -- Ye Chugui came off the bench to score in stoppage time of the second half, helping Guangzhou R&F beat Dalian Pro 1-0 in the 12th round of the Chinese Super League (CSL) here on Monday.
SUZHOU, China, Sept. 25 (Xinhua) -- Hebei China Fortune has secured the eighth spot in the Chinese Super League after beating Wuhan Zall 2-0 here on Friday.
BWF president Poul-Erik Hoyer Larsen and its secretary-general Thomas Lund said in a joint letter Friday that pushing back the tournament would affect the world rankings and next season's BWF Tournament calendar but it was the best option.