The Germans demolished Australia 4-0 - the highest-scoring game of the World Cup so far - as the Socceroos were reduced to 10 men by the dismissal of Everton midfielder Tim Cahill.
Serbia, in contrast, lost 1-0 to Ghana to make their qualification for the knockout stage more difficult.
But Zigic - who has agreed to join Birmingham - insisted they would not fear Joachim Low's side when they meet in Port Elizabeth on Friday.
"We need to forget about Ghana and go for it in the remaining two matches," said the newly-signed Birmingham striker.
"We won't be going for four points but for all six, although there are some permutations where a draw and a win would suffice for us.
"Germany were excellent against Australia but they had an one-man advantage for the entirety of the second half.
"It's all up to us right now and we have to believe we can qualify for the second round. We need to remain composed.
"We need to be careful and wait for our opportunity to come. We still believe in ourselves but the mistakes we made against Ghana cannot happen against Germany."
Winger Milan Jovanovic admits belief has been shaken by the defeat to Ghana.
The 29-year-old, who is set to join Liverpool this summer after his contract with Standard Liege expired, said: "The setback has affected our confidence because we expected to win the game against Ghana and most of us found it difficult to come to terms with the fact that we let ourselves down.
"We lost to a team which is not in our bracket in terms of quality and we now have to make amends against one that is superior, which is going to be very difficult.
"The Germans were as impressive as ever in their 4-0 rout of Australia, they were firing on all cylinders like a well-oiled machine and we'll have to play almost beyond our limits to beat them."
Wolves midfielder Nenad Milijas, whose place could to be under threat after a poor performance against Ghana, is pleased Serbia have the chance to put things right quickly.
"We should benefit from having to turn our attention to the game ahead, we have to pull our socks up," said the 27-year-old.
"Hesitation crept into the team during the Ghana game as we struggled to match our qualifying performances and we have to rediscover that form very quickly.
"Germany are obviously the favourites but we are hoping that our trademark defiance and the stinging criticism we took after losing to Ghana will inspire us to better things."