Have a closer look at SyncGene
Add as many accounts as you want to synchronize. You can add your Google, Exchange or iCloud account.
In the Filters dialog select Calendars and choose which calendar folders you want to synchronize.
In the Filters dialog select Contacts and choose which folders you want to synchronize.
In the Filters dialog select Tasks and choose the specific folders you want to synchronize.
You can see your synchronization progress as well as you can cancel synchronization at any time.
Check your synchronization status to know which accounts you have synchronized and the date of the last synchronization.
Backup & Restore
If you are not satisfied with the outcome of the synchronization you can back up your data to the point before synchronization.