@whitecloud Hi and welcome to the Forum.
Have a look at this thread which contains a useful checklist of things to do for a install.
Pay attention to #1 i.e. verify your dowloaded ZorinOS file checksum is correct.
I always use Unetbootin to create my bootable USB, which has never let me down, but is personal preference.
When you formatted the USB's did you do a full format, not quick format. Also what filesystem did you format them, FAT32?