distance calculation issue

[zzploveyou]

point a
utm.from_latlon(2,120)
(166223,221366,51,'N')

point b
utm.from_latlon(1,120)
(166072,110682,51,'N')

point c
utm.from_latlon(-1,120)
(166072,9889317,51,'M')

9889317 >> 110682

For point a and point b, We can calculate distance using the formula sqrt((x1-x2)**2+(y1-y2)**2). But how can i calculate the distance between point b and c since they have different zone_letters?

Is there any way that can converts latlons in the same coordinate / scale?