i make a drawing of my entirly plant with contents come from other companies. sometimes the z position of points are not correct (différent from zéro) and it causes some problem with the mesuring of distances. it causes also some problems on the screen because lines disappears during zoom + or -. 

is it possible to move all the z axis position to zéro or do i need to check all the thousands of points in my drawing?

thanks for your help

Sincerely

Jean-Paul