@manto6012 Hi and welcome to the Forum.
You said you checked the USB, but did you check the SHA256 checksum of the Zorin download?
If USB and download checksum are good, does the USB boot in Live mode. i.e. Try Zorin.
I would also have a look here: USB boot install
Also worth your time having a look at Swarfendor’s unofficial manual for Zorin 15.3 here: Unofficial Manual for Zorin 15