We are in the middle of doing this for a client right now. It does not appear to be particularly difficult.
But: You say "integrating" as if that in itself is a single act. Actually, integrating is different for every installation. It's not like connecting an exhaust manifold to an engine which only fits One Way with bolts. Connecting a CRM to a Dialer can involve an infinite number of links, data transfer conduits, triggers, and field maps.
So ... do you mean to push SALE leads from Vicidial to Zoho? Or do you want to call Zoho leads that have 60 days of inactivity but have never said "do not call me" on all the available phone numbers? Are your agents expected to log in to both systems, or Fronters in Vicidial and Closers in both Vicidial and Zoho?
It's all the same with Zoho as any other CRM. Just have to plan it out and then execute one piece at a time.