Villa's squad - the youngest in the Premier League - have had a rollercoaster ride in Lambert's first season in charge.
They are two places above the relegation zone after a wildly inconsistent season, but they are also through to the semi-finals of the Capital One Cup and the fourth round of the FA Cup.
They take on League Two Bradford in the first leg of their semi-final on Tuesday and - regardless of the level of opposition - Lambert says reaching the final would be huge for the club.
"For this club to get to Wembley again would be extraordinary," he said. "In a one-off game there you just never know what could happen.
"To get there I think every player would tell you would be absolutely phenomenal."
Asked whether it would surpass any of his previous achievements, the former Scotland international said: "I think it would, yes.
"I never view it as any great achievement on my own behalf. It's the players and the fans.
"I never really look at myself and think 'I'm going to do that' because it is irrelevant. The important thing is what happens to this club and the players."
Tuesday's hosts Bradford, who have already knocked out Arsenal and Wigan, are without a win in their last three games but Lambert expects a tough night.
"Of course it will be," he said. "It will be a different team to the one that got beaten by Barnet at the weekend. You have to withstand that and be ready for it.
"The Bradford lads will give it everything they have got to try to turn us over. If we do what we have been doing that of late and match that then we'll see what happens.
"It's always tough. Bradford have got nothing to lose and everything to gain. Obviously it is a two-legged affair. We'll go up there and we know it will be a really good atmosphere.
"I've been up there before and it will be a tough game for us. But if we play we have been of late, we'll see."