If you notice in the verse (فَإِنَّ مَعَ ٱلْعُسْرِ يُسْرًا)
"For indeed, with hardship [will be] ease." [94:5]
Hardship stars with "Al" in Arabic, making it definite, where as the word ease does not.
Shaykh As-Sa'di says:

"The word translated here as hardship appears in the definite form indicates that it refers to one hardship — the word translated here as ease appears in the indefinite form indicates that it is more than one, and one hardship can never overwhelm plural or repeated ease."