What would be the voltage V1? I tried voltage divider :
V1 = (R1+R2/(R1+R2)+(4 R0+ R3 +RT) )
As the voltage V1 does not have a common node with Vs, you can not simply use one voltage divider formula, you actually have 2 voltage dividers. By redrawing the circuit that becomes more clear:
So what you need to do is calculate the voltage of both voltage dividers. The voltage difference between the two dividers is V1.