عَلَى ٱلْكَـٰفِرِينَ غَيْرُ يَسِيرٍ
'Alal kaafireena ghayru yaseer
Sura üflendiği vakit, işte o gün, inkarcılara kolay olmayan zorlu bir gündür.
for those who deny — far from easy.
The pair of words carries the point: the verse before calls that day ʿasīr, hard, and this line answers with yasīr, its exact opposite, then negates it. Hardship is stated of the day itself, and ease is withdrawn from one group in particular, leaving the difference in how a single day lands on different people. Elsewhere the Qur'an uses yasīr for what costs God nothing.