If
Proto-Germanic *hurną is cognate to both
Proto-Slavic *sьrna (by centum - satem) and
Proto-Slavic *korva (by Grimm's law)
Why is
Proto-Germanic *kurnô can not be cognate to both
Proto-Slavic *zьrno (by centum - satem) and
Proto-Slavic *gorxъ (by Grimm's law)?
