I fail to see how? The ESP partition must be vFAT on GPT, in order for the BIOS to find it. Your BIOS doesn't speak ZFS.
The main partition can be whatever, but that's not typically available until after the kernel & initramfs are loaded. (As it is typically initramfs that does the prompt for the password, to decrypt it.)
The main partition can be whatever, but that's not typically available until after the kernel & initramfs are loaded. (As it is typically initramfs that does the prompt for the password, to decrypt it.)