How to connect multiple star points and ground zone together on PCB?
if you have 1 nanoVolt (1 billionth of a volt) of required trash floor, then this gets interesting.

Otherwise, sketch out ALL the charge flows, including charges from primary-to-secondary of all your transformers, and charges across the silicon of your ADCs as the digital interface strobes the ADC to extract data from the latest conversions, and map the feedback path from output opamp's VDD back thru the VDD tree to the first opamp that handles the sensor signal (This VDD tree feedback causes settling time issues.).

Since you have no spec for fidelity nor SNR nor settling or ENOB, I think you should just use 1cm wide GROUND foil and connect all the "GROUNDS" together.