What is the key difference between the openings of the two surahs?

Supplementary Practice 25 — Comparative Rhetoric of Sūrat az-Zalzalah and Sūrat al-ʿĀdiyāt

• Both begin with the same explicit imperative
• Az-Zalzalah opens conditionally in time; al-ʿĀdiyāt opens with an oath and fast succession
• Az-Zalzalah begins with an oath and al-ʿĀdiyāt with negation
• Both begin with the same expressed conditional answer