Aiden Markram excels in his 'toughest' Test innings

South African opener Aiden Markram, who had a sublime start to his Test career, has revealed the 'toughest' innings he has played so far.

The 23-year-old said that facing the pink ball in twilight conditions against Zimbabwe on Boxing Day was the most difficult challenge he has faced until now.

"There were a few factors that made it quite difficult ... the pink ball being one. Today was probably the toughest it's been for me so far," Sport24 quoted the 23-year-old, as saying.

He also shared about the difficulty he faced in switching formats, after having recently appeared in the RAM SLAM T20 Challenge.

"It's not always easy to just jump format to format like that. I am still very inexperienced and it was a bit of a challenge for me," he said.

Having scored 97, 15, 143 and 125; a total of 380 runs in his first four innings against Bangladesh and Zimbabwe; Markram is already making waves in Test cricket.

However, the true test of his caliber will be the upcoming series against India and Australia.

South Africa, who are playing their inaugural day-night Test match against Zimbabwe, declared their first innings at 309-9 on Day One.

At stumps of the first day, Zimbabwe were reduced to 30-4, still trailing South Africa by 279 runs from their first innings.

Pacer Morne Morkel picked up three wickets while Vernon Philander also chipped in with one wicket.