Which of the following pairs of cities are in the same time zone?

The above figure shows the time taken in hrs:min to travel between two consecutive cities both for upward and downward journeys.

The difference in time between two consecutive cities will be the average of the difference in time taken for upward and downward journeys.

So, the difference of time for different consecutive pairs can be found as below:

Z-Y: 

For both up & down motions time difference is 0. Hence, Z & Y are in same time zone.

Y-V:

Time taken for travelling from Y to V is less than that of from  V to Y with a difference of 4 hrs. Hence, Y is 2 hours ahead of V.

V-S:

Time taken for travelling from V to S is less than that of from  S to V with a difference of 6 hrs. Hence, V is 3 hours ahead of S.

S-R:

Time taken for travelling from S to R is less than that of from  R to S with a difference of 2 hrs. Hence, S is 1 hour ahead of R.

As shown above, only cities Zut and Yag are in same time-zone.

Hence, option C.