No worries there my good friend. You're doing perfect.
Just as I thought you have enough space to use as a backup.
You can use gparted to create a separate partition of 200GB.
After this you can startup the file manager, so you can manage your backup data. Copy the files you want to keep to the newly created partition.
When done you can start the installation and make sure you install the system to the first partition which already has Zorin.
You will have to format this and install the system once again.
Hope I am clear enough?