zero-sequence circuit of the three phase transformer question
You are closer than you imagine.  

Label your top node as the "zero sequence neutral bus" for completeness, so you don't forget. 

The M-P transformer has identical winding configuration as the N-Q.  Your treatment of the N-Q transformer is correct.  Apply that to your M-P.

The rest of what you have done is correct.  You need to add your V-X transformer and your S-U transformer as well as your remaining overhead line.  They will end up forming an unreachable island - but your teacher probably would like to see it for completeness.

When you are finished with the complete diagram, i would also recommend drawing a 2nd diagram showing only the relevant impedances. Get rid of the stuff that will not matter to any fault calculations.  e.g.  I would simply remove your X0T4 impedance from the diagram to keep it clean (your treatment of the R-T transformer is correct, but not worth adding to your diagram since no zero sequence current can circulate in either delta so it will never affect fault calculations).

p.s.  You should label your neutral reactors as 3Zn as well since our symmetrical component model calculates V0 and I0 quantities.  3I0 flows in these elements so to correctly account for them in this model we multiply their impedance by 3.