In this case, you don't want to use mp64 to generate a wordlist or pipe anything to hashcat. Instead, you want to use it to generate rules.
Code:
$ mp64 -1 ?l?d?u "^?1^?1" >prepend-ldu2.rule
$ hashcat -m XXXX -a 0 -w 3 -r prepend-ldu2.rule hccapx
~