I believe you answered part of your own question. I don't know how you did it, but to install zorin in legacy while windows is in efi is nearly impossible. Legacy uses the mbr structure which limits the number of primary partitions to four and the rest are extended partitions(again with a limit). Efi uses the gpt structure allowing for many partitions, all bootable of necessary. These structures are so different they don't work together. That may be part of your problem.
As for resizing partitions, did you ensure fast boot and secure boot were off in the bios? If it's on the same physical drive as windows you may need to boot windows, press windows key+x -> power options -> choose what happens when i close the lid or choose what happens when i press power button -> left click the shield symbol and accept to allow changes in bottom half of screen. Uncheck fast boot. Save and exit windows.
Also, never resize a partition that is bootable while your in it. This can have disastrous effects and make your system un-bootable. I'll do a little research, but you will probably have to reinstall.
Boot from your live usb, access the try zorin option.
Under the app menu (zorin button) open boot repair.
Under GRUB options select "purge GRUB before reinstalling it"
This should reinstall grub, after removing the broken version.
Reboot and try to enter zorin.
If this doesn't fix the issue you will most likely have to reinstall. Whatever iso software you are using, please reformat your usb to use efi option (gpt) and this will avoid future headaches. Legacy mode isn't necessary unless you are installing to older hardware.