I dont asnwer what to do with the wires crossing
It looks like the resistors do not cross at the center. Normally a joining point would have a shaded circle on it, but this isn't used elsewhere in the circuit, so it probably wasn't used at the center either.
So, I would take it that the 4 resistors join at the center and do not cross over.
Looks like a lot of simultaneous equations.
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