Divisionof labour is not the debate - that's merely the function of a brawn - the brain can't really do several tasks all together - it has to cheat.
I suspect we are having a semantic problem here.
the brain is capable of processing multiple independent inputs and processes simultaneously, partly as a result of its anatomy and hardwiring, partially as a result of higher synthetic division of labor.
the mind is not conducting rapid serial processing - it is accomplishing simultaneous parallel processing.
this is multitasking.