[quote="Divine Phoenix"]If Jinzo and Jinzo - Returner are sent to the graveyard simultaneously would Jinzo be able to be summoned by Jinzo - Returners' effect??[quote]
Yes, Jinzo-Returner's effect doesn't activate until it hits the graveyard, if both monsters are sent to the graveyard by the same card effect, (such as with Future Fusion) then Jinzo is a legal target for Jinzo-Returner.
It's a nasty combination no doubt.