Dallas is 11.75 hours behind Kathmandu
There is no standard 8-to-6 overlap. Someone joins early or late.
Given Dallas is 11.75 hours behind Kathmandu, the realistic answer is that there's no convenient shared slot during normal business hours. Catch the edges of the day: the last hour for Kathmandu or the first hour for Dallas is usually the least painful option. Heads up: because Dallas changes its clocks and Kathmandu doesn't, the difference moves by an hour twice a year. Confirm the overlap around the DST switch.