Complex sentence: Local military experts have said that it was neither necessary, or affordable for Taiwan to deploy THAAD because China is threatening Taiwan with short-range missiles, whereas THAAD is designed to shoot down medium and long-range missiles.
Split into simpler sentences: Local military experts have said that it was neither necessary, or affordable for Taiwan to deploy THAAD. This is because China is threatening Taiwan with short-range missiles, whereas THAAD is designed to shoot down medium and long-range missiles.