Chris Hughton's side had surrendered first place following Derby's 2-0 victory at Hull on Friday, but 34-year-old Zamora's decisive intervention at the Amex Stadium ensured the Seagulls leapfrogged their promotion rivals to reclaim pole position.
Solly March put Brighton in front in the 17th minute before Jon Toral headed an equaliser four minutes later for sixth-placed Birmingham.
Former Tottenham and West Ham striker Zamora, in his second spell at the club where he made his name, extended Brighton's 18-match unbeaten start to their league campaign when he scored from close-range after March's effort had been blocked in the 47th minute.
"Bobby has a certain know-how and he knows what he can't do," Hughton said.
"He's not missing a lot of chances. The opportunities he's had, he has put away."
Middlesbrough moved into second place as they claimed a sixth win from seven matches in all competitions by beating struggling Huddersfield 2-0 at the John Smith's Stadium.
Adam Clayton's deflected ninth-minute effort put Boro in front and despite a strong performance from the hosts, the lead was doubled by Emilio Nsue with six minutes left.
"It was not a good performance but sometimes games are like that," Middlesbrough boss Aitor Karanka said.
"Huddersfield looked like the top team, not us. Huddersfield played really well and I expected that."
Ipswich are seventh after a 3-0 win at Charlton that was clinched by two goals from Daryl Murphy and one from Freddie Sears.
Fifth-placed Burnley extended their unbeaten run to nine matches as Matthew Connolly's 93rd-minute own goal salvaged a 2-2 draw at Cardiff.
Lucas Joao's seventh goal of the season came six minutes from full-time to give Sheffield Wednesday a 2-2 draw at Blackburn.
At the bottom of the table, Rotherham secured back-to-back victories with a 3-0 home win over Bristol City.
Nottingham Forest claimed just a second win in 11 games with a 3-1 victory over Reading at the City Ground.
Matej Vydra's cool finish in the 14th minute gave the Royals the lead but Forest stormed back as Chris O'Grady levelled from a Ryan Mendes assist.
Mendes was heavily involved in the goal that put Forest ahead as he led a counter-attack and played in Nelson Oliveira to score after half an hour's play.
Oliveira added Forest's third in the 49th minute and the hosts held on despite Jack Hobbs' dismissal in the 66th minute.
Charlie Austin came off the bench to give QPR a 1-0 win over Leeds with his 58th minute strike at Loftus Road.
Ross McCormack notched his 12th of the season to rescue a 1-1 draw for Fulham at home to Preston, while Wolves and Milton Keynes Dons shared a goalless stalemate at Molineux.