A process for upgrading vacuum residuum and vacuum gas oil hydrocarbons is disclosed. The process may include: contacting a heavy distillate hydrocarbon fraction and hydrogen with a zeolite selective hydrocracking catalyst in a first ebullated bed hydrocracking reaction zone to convert at least a portion of the vacuum gas oil to lighter hydrocarbons. Contacting a residuum hydrocarbon fraction and hydrogen with a non-zeolite base metal hydroconversion catalyst in a second ebullated bed hydroconversion reaction zone may produce a vapor stream containing unconverted hydrogen, acid gases and volatilized hydrocarbons which may be fed along with the vacuum gas oil in the first ebullated bed hydrocracking zone.