If you want to install Archlinux on ZFS, you need to deal with the ZFS licensing problem. The kernel module isn't included in the default archiso image, you need to include it into a custom archiso image to be able to install ZFS.
I wrote an article about archiso netbooting.
This script lets you include the zfs kernel module on any archiso image without creating a custom one.
The Archzfs unofficial user repository offers multiple ways to install the ZFS kernel module.
We can install precompiled module with zfs-linux package or compile the zfs module using DKMS method.
In order to build the module, DKMS needs the linux-headers package for the running kernel.
It extracts running kernel version and try to find a matching ZFS module in Archzfs repositories.
If it doesn't, it fallbacks to the DKMS build of the ZFS module.
In that case, the script uses Arch Linux Archive to install the linux-headers package required for DKMS.
Boot on any archiso system, and run:
curl -s https://eoli3n.github.io/archzfs/init | bash
To run the script in verbose mode, use:
curl -s https://eoli3n.github.io/archzfs/init | sed 's- &>/dev/null--' | bash &> debug.log