as the two guides from https://hashcat.net/wiki/?id=mask_attack...mask_files and https://hashcat.net/faq#what_is_a_hashcat_mask_file already emphasize, you must specify all the hcchr and custom charset directly within the mask file (.hcmask)
my.hcmask
my.hcmask
Code:
charsets/special/German/de_ISO-8859-1-special.hcchr,?l?u?d?1,?a?a?a?a?2?2?2?2
Code:
./hashcat64.bin -m 0 -a 3 hash my.hcmask