Blues took a 29th-minute lead on Saturday as Marlon King notched his fifth goal of the season before Stephen Crainey levelled for the home side and his fellow full-back Neal Eardley produced a magnificent drive shortly before the hour to put the Seasiders in front.
But Zigic claimed an 87th-minute leveller shortly moments after he had headed a golden chance past the post at Bloomfield Road.
The point edges Blackpool into the play-off places at the expense of Hull on goal difference, with their opponents a point further back
Lomana LuaLua had been a surprise omission from Blackpool's matchday 16 for the 2-2 draw with Middlesbrough after missing a team meeting.
He returned to Ian Holloway's side in attack alongside winger Matt Phillips, making a first start since his loan spell at Sheffield United, while Eardley came into the Seasiders defence in place of the injured Craig Cathcart, with Alex Baptiste reverting to centre-back.
Birmingham boss Chris Hughton made one change from the side that beat Burnley in midweek, as Wade Elliott replaced Zigic.
And the game's first chance fell Elliott's way after Chris Burke sprung the Blackpool offside trap to collect King's pass.
His cross found Elliott, whose shot from inside the area was deflected to safety.
Phillips responded for the hosts, firing narrowly wide at the end of a probing run.
Blackpool goalkeeper Matt Gilks displayed inspired form at the Riverside Stadium last week and he produced another magnificent stop to tip King's header from Burke's 17th minute cross over the bar.
However King won the next duel between the two when he was played in by Elliott and slotted Blues into a 29th minute lead.
Blackpool's response was instantaneous. LuaLua's pass found Crainey marauding in the Birmingham area and the Scotland international was able to prod past Boaz Myhill.
King then headed another Burke centre into the side netting and Crainey's countryman Barry Ferguson could have sent Holloway's men in ahead at the break when he fired wide from 12 yards.
The Seasiders started the second period in the ascendancy with Phillips slicing wide following Gary Taylor-Fletcher's knockdown.
In the 57th minute, Blackpool took the lead in spectacular fashion, as LuaLua squared and right-back Eardley claimed his first goal for a year by sending an unstoppable 25-yard drive swerving into the top corner.
Phillips' enterprising wing play was keeping Birmingham on the back foot, but when Blues attacked Burke's trickery was to the fore and the 27-year-old drew another superb fingertip save from Gilks.
Zigic was introduced in the 71st minute in place of the largely anonymous Jean Beausejour, and his first significant contribution was a horrible miss, nodding wide from point-blank range after getting on the end of Keith Fahey's cross.
But Blackpool did not heed the warning and the big Serbian was on hand to steer Jonathan Spector's centre beyond Gilks with three minutes remaining.