"Once per turn, during your opponent's Main Phase or Battle Phase: You can activate this effect; immediately after this effect resolves, Synchro Summon 1 Synchro Monster using "Cosmic Dragon" monsters you control only (this is a Quick Effect)." effect is a Quick Effect that can only be activated during your opponent's Main Phase or Battle Phase. (This effect does not target. It cannot be activated during the Damage Step.)[1
That is the ruling for The second effect of Yang Zing monsters. Something i'm looking into. The effect is a quick effect which allows me to synchro summon using Yang Zing monsters only. The ruling doesn't state that this effect needs a tuner to resolve.
My question is, do i need a tuner? By the ruling it doesn't seem i do, since it's the effect of a card. I'm not sure however.