Just found out that it is possible to boot your piZero 2W from USB key
1) download & install raspberry OS and boot
2) copy /boot/bcm2710-rpi-3-b.dtb to /boot/bcm2710-rpi-zero-2.dtb
3) add 'program_usb_boot_mode=1' to /boot/config.txt
4) reboot raspberry OS
5) now you can dd whatever image you want to your USB key and it will boot (I tried with picore 3.1.0 img)
Obviously you'll have to use an OTG cable and you might want to remove the sdcard
Regards,
Pengo