I just found this information on the FXCM microlot website:

Some accounts have a log in that is different from the account number. Please be sure to be typing the log-in information, and not the account number in the log-in field. Your log-in information and account number was provided in the registration email sent to you when your account was first opened.

So could you include the option to specify the account number in the next release of Zorro? Only then will I be able to trade using Zorro.

Thanks
Guiom