Complex sentence: On both sides of it, removable ejectors for seamines could be mounted and behind the pilothouse was a rear facing ZU-23-2 23 mm gun for airdefence.
Split into simpler sentences: On both sides of the pilothouse, removable ejectors for seamines could be mounted. On the aft deck, a rear facing ZU-23-2 23 mm gun was mounted for airdefence.