ZIO is normally held in November-December. ZIO-2021 was held on 19 December, 2020.

ZCO is normally held in November-December. Due to CoViD-19 constraints, ZCO-2021 did not take place.

Hello Student

Zio is a zonal informatics Olympiad Olympiad.ZCO

Is a zonal computing Olympiad for appearing iOi

Means international Olympiad of informatics one should have to to qualify in any of the olympiads like ZIO&ZCO.

ZIO is not a programming exam it can be  written on paper but ZCO is a programming computing exam and the exam will be through computer.

ZIO  is a n easier examination than ZCO. After qualifying in any of theZIO orZCO candidate can appear for the Indian National informatics Olympiad i.e.INIO which is a a tough  exam one.

Hope this helps.