question

The answer will depend partly on if you have 'drop in' lithium batteries or externally managed BMS batteries. Assuming you have 'drop in' batteries you can use VE.Smart network over bluetooth to synchronise the charge between the two IP-22 chargers. https://www.victronenergy.com/media/pg/VE.Smart_Networking/en/index-en.html If you have managed batteries you will need to look to the BMS system for synchronised charging options.

I have 4 Expert Power EP12100 Lithium, they each have their own built in BMS that protects batteries from overcharge, deep discharge, overloading, overheating, short circuit, and excessive low self-discharge rate, but there is no external BMS, so guess this is called “drop in”. So the two Smart IP-22 chargers and the BMV 712, will see each other on Bluetooth App and synchronize, there is no additional wiring? Also The 12v + and - outputs from each Charger just go directly to the 12v House + and - Bus right?

Yes the batteries are often referred to as 'Drop in' batteries as you can use them to replace existing batteries without having to do the full BMS install. The bluetooth VE.Smart network will transmit battery voltage and temperature from the BMV-712 to the IP22 chargers as well as the synchronisation between the two chargers - no additional wiring required. The charger hooks up to the battery as you described - specific instructions are in the manual. If you haven't done so already download the VictronConnect App and have a look at the 'demo' products available in the demo mode. It won't able to show the syncronisation between IP22 but will give you a good idea of the other functionality. Please note that while the DC/DC charger that you have already installed has bluethooth it does not support VE.Smart.