IaaS = you manage VMs. PaaS = platform runs app (App Service). SaaS = ready software (Office 365). ShopNest API on App Service is PaaS; a custom VM jump box is IaaS.
Zensar rounds often probe: Digital engineering.
Themes commonly reported in public MNC interview experiences (AmbitionBox / LinkedIn / Glassdoor-style). Practice aloud; keep answers this short in the real round.