Sony Airplay Speakers LAN port connection vs Airport Express standalone Airplay receiver only

I think something is being lost in translation.

From your diagram it looks like you're trying to "connect" the Sony speakers to the Airport Express via ethernet, correct? While this will work to bridge the LAN to your wireless network it WILL NOT allow the Airport Express to push audio to the Sony speakers. The ONLY WAY to get sound out of the Airport Express is to use the 1/8" jack.

My understanding is that those two Sony speakers are Airport compatible themselves. If you want to stream audio to them simultaneously from an iOS device, yes, you will need to wait for Airplay 2 (assuming Sony updates the firmware to support it).

Airplay 2 must be present on both the transmitting device and the receiving device to allow the advanced functionality like multi-speaker streaming.

the airport express works by having a minijack connector and when one connects an minijack with a speaker in the other end or a stereo or a headset it acts the rule of audio output source

in itunes on a computer it will show up as a speaker one can play audio out of

in itunes on a computer one can choose several speakers that the computer will play from

currently I believe ios devices only let you play from one at the time

the sony speakers if they support airplay audio will act the same as an airport express with a speaker connected to it by 3.5mm minijack connector

it sounds like your impression of what the airport does contains something about it using other airport audio devices to play out of but it does not work like that

some other threads has people saying the existent airport express may not support airplay2, if that will be the case I know not