The Zero has a debugger chip on the pcb. Since Arduino is not owned by Microchip / Atmel it has to buy the UC32 silicon chip and pay a licence for the debugger firmware.In the Old Days you paid several hundred dollars for a JTAG/SWD debugger like J-Link.Then Manufacturers started to sell Evaluation boards with an onboard debugger chip.It costs the Manufacturer about $1 for the hardware. And ARM provide the software code for free. So it does not cost the Manufacturer anything much to provide this functionality.For the User it is brilliant. An ST Nucleo board for about $15, An NXP board for about $20, a Microchip Curiosity board for about $10. Or even the Atmel XMINI (with SLOW debugger) for $8.A far cry from the Olden Days when you paid $100s for an Evaluation and an extra $200 for a debugger.Unfortunately the Chinese can't buy the debug chip. So we don't get cheap Zero clones. But we do get cheap Due clones. And you can use the SWD interface with a $3 ST-Link clone dongle if you want. (Obviously not supported by AS7.0)David.