His Shinigami powers are mixed with hollow powers in one Being( Hichigo who is the spirt of the big sword) and the small sword is his Quincy Powers ( Fake Zangetsu )I think one is hollow release and the other one is a shinigami release and there's going to be a 3rd Quincy release.
I re-read the chapter where Ichigo's Zanpakuto is reforged. Ichigo said the both are Zangetsu. And the guy how reforged asked him how those Zangetsu are? So it must be his shikai, because his bankai will be Tensa Zangetsu.