ZESCO won the first leg 2-1 in Ndola after a brace from Jackson Mwanza, while Khama Billiat grabbed a late away goal largely against the run of play.
The Zambians have displayed exemplary form at home with five wins in six matches during the competition, but their form on the road hasn't been as convincing - Team Ya Ziko have lost twice on their travels.
Nonetheless, while George Lwandamina's side are more vulnerable away from home, Mosimane is still of the belief his side face a stiff challenge in overturning the first-leg deficit.
He told reporters: "We have been under pressure the whole week and we're used to this pressure and have experience in this space. We have another big one on Saturday against all odds!"
The Brazilians face the Zambian champions in the second-leg semi-final of the Champions League at the Lucas Moripe Stadium on Saturday. The action gets underway from 19:00.