So you intend to dual-boot alongside Windows.
How did you try to install Zorin. Did you use the "Something else" method?
Can you post a screenshot from Gparted, showing your disk partitions?
Maybe also take a look at this thread: USB boot install
If new to Linux and Zorin, @swarfendor437 's "Unofficial Manual for Zorin 15" is still available to download. See here: Unofficial Manual for Zorin 15