If you plan to enter Tibet Autonomous Region by car through the Nepal-Tibet border to Zham, then, indeed, the individual Chinese visa will be canceled, since in this case it is necessary to open a special group Chinese visa in addition to the Permit to enter the TAP, if you fly from Kathmandu to Lhasa, the capital of Central Tibet, then you need to pre-register a Chinese visa in order to obtain an entry permit..In both cases, you should contact the travel company, because "wild" tourism in the TAR is banned and the route of stay there, including the services of a local guide accompanying, still need to be booked through the travel agency .