Complex sentence: Pakistan currently has four cruise missile systems in service, of which, two are nuclear-capable cruise missiles: the air-launched Ra'ad and the ground/submarine launched Babur, surface ship-launched Harbah and the ground-launched Zarb.
Split into simpler sentences: Pakistan currently has four cruise missile systems in service, of which, two are nuclear-capable cruise missiles: the air-launched Ra'ad and the ground/submarine launched Babur. The other two are surface ship-launched Harbah and the ground-launched Zarb.