While preparing for ZCO in particular, and INOI subsequently I wonder the best way to utilize the time left for the exam. With this in mind, I wanted to take help of the experienced about which topics should I particularly study for ZCO and INOI. I know that the areas of concept on which the questions are based are different for the both. Please specify for each, and tell which topics do occur most frequently in ZCO and INOI separately and what all things are a must to prepare for.