Compressed Raspberry Pi ISO from Linux

Doing this clears up "empty" space on the drive so the iso get's properly compressed:

1.) Clear up Raspberry with temp file:
dd if=/dev/zero of=/tmp/zero1.tmp bs=1048576
2.) Delete tmp file:
rm -f /tmp/zero1.tmp
3.) Take SD card to another computer and create a compressed iso:
sudo dd bs=4M if=/dev/ | pv | xz > Pi.img.xz

Example: Currently have a 64GB iso compressed to 1,2GB. Actual drive usage of the 64GB iso is 3,6GB.

Thanks to:
https://www.locked.de/space-effective-backups-of-raspberry-pi-sd-cards/