QPR came under intense pressure after Gary O'Neil was sent off for a foul on Johnny Russell on the hour mark, but Zamora seized on a poor clearance from Richard Keogh to score the decisive goal.
Zamora hit a play-off winner for West Ham United in 2005 and was thrilled to repeat the trick to take QPR back to the Premier League just 12 months after they were relegated.
Asked what was running through his mind as the chance came his way, the striker told Sky Sports: "Just take a shot and hit the target. It sat up perfectly and it is a magnificent feeling. I never thought it would happen again.
"I am over the moon for this set of lads. I scored the winner to get West Ham up so this is equally important.
"We have dug in over the last couple of months and we've shown a great togetherness to fight until the end."
Defender Richard Dunne added: "It's amazing. It's been such a long hard season.
"We know how good we can be when we worked and we've worked really hard.
"When the time came Bobby was there to finish it.
"It's what we've been aiming for all year and we got there through the play-offs."
Charlie Austin was the only member of QPR's starting XI not to have previously played in the Premier League and he is relishing the chance to play in the top flight, having joined the club from Burnley last August.
"The lads have given me a bit of stick about that and I am so chuffed to get there," said Austin.
"Obviously I left Burnley in the summer to try and get to the Premier League and they have done it so I am happy for them, but I was all about getting QPR to the Premier League.
"I am so excited about going to the top grounds and playing against the best players."
Austin added: "Of course I felt sorry for Derby but that is football, there's got to be a loser."
Reflecting on his dismissal, O'Neil pleaded for forgiveness from the fans as he says he only dived in on Russell to try and avert a goal.
"I am fine now. I was obviously devastated at the time but it was a split-second decision," said O'Neil.
"I knew I was getting the red if I fouled him but I have never been sent off before and I hope the fans don't hold it against me."