To use max XZ compression and all cores add export XZ_OPT='-T0 -9' to the end of your ~/.bashrc file. To use all cores add export XZ_OPT='-T0' to the end of your ~/.bashrc file. To use max XZ compression add export XZ_OPT='-9' to the end of your ~/.bashrc file. Then exit terminal and go back or source ~/.bashrc