I want to clear about disk partition !
Hello @enrhasan and welcome to the Forum.
Are you intending to install Zorin as the only operating system on your hard disk or do you want to dual-boot with an existing operating system that is already installed on it?
You will need to create partitions on your disk for Zorin, but that may not necessarily mean you have to format or erase the whole disk.
It would be good if you could indicate the spec of the PC so that people here can advise you better.
Also you can try Zorin by running it from a Live USB stick. Have you already done that?
Finally, you would be wise to have a read of @swarfendor437 's unofficial manual for Zorin 15 which includes advice and details for installation. You can find the manual here:
Get back to us with your questions and I am sure we can help you out.