indeed, sync cable not needed in your setup as volume and switch on/off of the speakers is done through PL.

This delay is strange, as it should work as you did connect the whole thing, to me.

Are you sure that the delay is not coming from the distance of some speakers from your listening position ? you need to position yourself at equidistance from the 4 speakers, at least try this to check if my assumption is correct

I would double check that the whole Option settings (V-OPT, A-OPT and L-OPT) is correct on every item, maybe you have some speakers using the digital connection, maybe others using the Powerlink from the TV via the Masterlink. It would explain such a noticeable delay