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You could use that to delete the Zorin Partition, yes. And it would be neccessary to delete the ''ubuntu'' Entry in BIOS because You could get Issues when starting the Machine.
But in Your Case would be need to clear Questions before:
- Is Your BIOS in UEFI or Legacy Mode? Depending on that Your bootable USB Stick should be in GPT (for UEFI) or MBR (for Legacy).
- What Tool did You use to create the bootable USB Stick?
- Did You made a Back-Up from the Data of Your Zorin Installation? If You should need the Data I mean.