Can any one tell me if tOPCODER Will help in ZIO,IOI?
Surely it will help all u need to find the algorithms that are of importance to you.
Best way to prepare for IOI is working with syllabus of IOI and training on similar tasks and contests in similar format.
But any practice will help you to improve, so TopCoder will help you with preparing for IOI, for sure - same as CodeChef, CodeForces and other sites.