Complex sentence: During the Thirty Years War, the imperial family moved to Linz, and here she died of poisoning during her last pregnancy, her daughter (Maria of Austria) was still alive, and was born by a cesarean, but died soon after.
Split into simpler sentences: During the Thirty Years War, the imperial family moved to Linz, where she died of poisoning during her last pregnancy. The child she was carrying, Maria, was still alive, and was born by cesarean section, but died soon after.