M3i Zero works fine on JAP, US & EU 3DS console with the new released version has been confirmed. 10-6-2011
Please be sure to update the M3i Zero to Core 2.0.2 to support 3DS new firmware Ver. 2.0.0-2U/E/J
If you have SD card compatibility issue on 3DS, try to use M3GUpdaterPlus_142.nds to upgrade with compatible SD card or on NDS/NDSi to complete.
Core for M3i Zero only:(10-6-2011)
M3i Zero Core data file V1.8.2 ( download it )
1.Support M3i Zero Model:GMP-Z003 & old Models;
2.Support 3DS Japanese firmware Ver. 2.0.0-2J;
Support 3DS USA firmware Ver. 2.0.0-2U;
Support 3DS European firmware Ver. 2.0.0-2E;
Support iDSi Chinese firmware V1.4.3C;
Support NDSi/NDSi LL Japanese firmware V1.4.2J;
Support NDSi/NDSi XL American firmware V1.4.2U;
Support NDSi/NDSi XL European firmware V1.4.2E.
1. All machines are upgradable: even your machine has already been in firmware 1.4.2. And no need to find another bootable machine to perform the upgrading process.
2. risk-free: flash card will not be damaged even the upgrading process is not successfully.
3. fast and easy to update
just plug in the "programming cable" and wait for about 30sec.
For details please read the PDF file below.

M3i Zero firmware Upgrade Manual(*.pdf file) ( click to view )
If you have SD card compatibility issue on 3DS, try to use M3GUpdaterPlus_142.nds to upgrade with compatible SD card or on NDS/NDSi to complete.
(For M3i Zero GMP-Z003 only) (Download and Details)