What do you know. It turns out that Highlander II (Officially subtitled “The Quickening”, unofficially subtitled “Oh my god, what an awful film, what the hell were they thinking?”) has a different, Director’s Cut version, subtitled “The Renegade”, in which all references to the Planet Zee and the immortals being aliens from outer space are removed, and a different explanation given for all the mess.
Might even turn the movie into something more bearable, because other than the script, the movie had some really cool bits.