Zen’s aimed at enlightment. Tantric Buddhism’s practice of Mahayoga,namely generation stage, leads to realization of emptiness by visualizing and practicing Yidam. Practice of Anuyoga, namely completion stage, results in realization of emptiness by mainly practicing nadi(tsa),bindu(tigle).By directly practicing nonduality of compassion and emptiness, practice of Atiyoga brings in realization of emptiness finally. Among all of these Dharmas, it’s the easiest and fastest way for practicing Atiyoga, namely Trekcho and Togal,to realize emptiness, this is our Mahasandhi’s extraordinary pith instruction.