Try this method brother @jefe
Even I'm also faced this problem. I have dual booted my laptop. Windows 10 and Zorin. After installing Zorin OS.
I have tried using cmd(DISKPART), but there is no result same problem arises. At last my friend @Tamil only said me this technique.
I Logged on to Windows 10. Download and run poweriso as admin and continue it as TRIAL then go to TOOLS --> Clean USB Drive after that format the PEN DRIVE. Now, the USBs running fine for me. I don't know maybe this will work for him also I'm thinking.
Steps:
- Insert the flash drive into one of the USB ports.
- After installation, run powerISO as an administrator. To do this, right-click on the powerISO desktop shortcut and click on Run as administrator. A confirmation dialog that says “Do you want this app to make changes to your device” will be displayed. Click Yes to continue.
- When powerISO is opened, wait for 5 seconds and click on continue unregistered.
- From the navigation bar, open Tools and click on clean USB drive…
- Select the USB flash drive with the space issues. If the drive is not listed, click on the refresh icon and check the list again

- Then click on clean USB drive.
- The cleaning is completed successfully, but at this point, the USB drive will not show its size.
- To complete the process, right-click on the flash drive from the file explorer and click format.
- In the file system section, select FAT32, mark quick format and click OK.
- The flash drive will be formatted successfully and the original drive size will be restored.