The Mpumalanga-based side once again proved they are a force to be reckoned in the competition, stunning Usuthu with an early goal before sealing the upset late in extra time to secure their place in the semi-finals, after the home side equalised in the second-half.
Casric arrived in Durban full of confidence after already eliminating Orlando Pirates in the previous round, a warning sign that they were capable of troubling top-flight opposition.
They lived up to that reputation with a bright start to the encounter.
The visitors took the lead in the 12th minute when Lelethu Skelem slipped a perfectly timed pass to Mfundo Thikazi. The winger kept his composure and fired a low shot past goalkeeper Darren Johnson to give Casric an early advantage.
Moments after conceding, AmaZulu suffered another setback when Johnson picked up an injury and was forced off the pitch, with Richard Ofori coming on as his replacement.
Despite the early blow, Usuthu gradually settled into the match and began pushing forward in search of an equaliser. However, Casric goalkeeper Tshigwana Mthombeni was in inspired form, producing several key saves to keep his side ahead.
AmaZulu came close to leveling matters in the 40th minute when Athini Maqokolo found space inside the box, but Mthombeni reacted quickly to make another impressive stop.
Casric nearly doubled their lead just before the break when Thabang Rakwena was sent through on goal, but the attacker dragged his effort wide with only the keeper to beat.
The first half ended amid loud appeals from the AmaZulu players and supporters for a penalty after a suspected handball by a Casric defender.
The hosts responded strongly after the restart. Just minutes into the second half, Hendrick Ekstein brought AmaZulu back into the contest when he finished calmly to make it 1-1.
The equaliser lifted the home side’s confidence, and they began to dominate proceedings. Tebogo Mashigo came close to giving the KwaZulu-Natal outfit the lead in the 63rd minute but fluffed his shot at a crucial moment.
Casric, however, remained dangerous on the counter-attack, although poor decision-making in the final third prevented them from restoring their lead.
With neither side able to find a winner in regulation time, the match was forced into extra time.
Chances were scarce during the additional period as fatigue and strong winds made conditions difficult. Ofori was fortunate to escape with only a yellow card after handling the ball outside the box to stop a dangerous Casric attack.
Just when the game appeared destined for penalties, Casric struck the decisive blow in the 115th minute. Substitute Decide Chauke found space inside the box and calmly finished to make it 2-1, sparking wild celebrations among the visitors while leaving AmaZulu supporters heartbroken as they marched on into the semi-finals.
Sekhukhune United coach Eric Tinkler says he was proud of his players' performance despite their "heartbreaking" shock Nedbank Cup quarter-final loss to Milford FC.
Milford FC continued the giant-killing theme of this season's Nedbank Cup with a 3-2 penalty shoot-out victory against Sekhukhune United in their quarterfinal clash at the Peter Mokaba Stadium.
AmaZulu head coach Arthur Zwane believes his side must tread carefully when they face Casric Stars in their Nedbank Cup quarter-final encounter at Moses Mabhida Stadium on Saturday.
TS Galaxy assistant coach Bernard Parker believes the club has a real opportunity to mount a serious Nedbank Cup challenge this season, but insists they must first avoid an upset.
