Complex sentence: Observing that the green meteorite endowed Super-Soldier, Luthor creates a serum from it, which he then injects it into himself; the result greatly extends his own lifespan, but inadvertently turns him into the cadaverous Green Skull.
Split into simpler sentences: Observing that the green meteorite endowed Super-Soldier, Luthor creates a serum from it, which he then injects into himself. The result greatly extends his own lifespan, but inadvertently turns him into the cadaverous Green Skull.