Complex sentence: Little is known about their development process apart from that they used Sage IV computers, preferred to develop for the ZX Spectrum's Z80 microprocessor, and often outsourced development for other platforms, such as those that ran 6502 microprocessors.
Split into simpler sentences: Little is known about their development process apart from that they used Sage IV computers. They also preferred to develop for the ZX Spectrum's Z80 microprocessor and chose to outsource development for other platforms, such as those that ran 6502 microprocessors.