All the teachings of the Buddha are of one taste ―all lead to the truth, all arrive at the truth. Although there are different Yanas (vehicles), they neither contradict each other nor reject the basis of each other.
The views that are fully made clear in the introductory Yanas are neither changed nor rejected in the more advanced Yanas, but accepted as they are. The points that are not made completely clear in the introductory Yanas are made clear in the more advanced Yanas, but the basic structure is not changed and none of the points that are already clear are contradicted.
Therefore different Yanas and Lineages do not go in different directions and they do not arrive at different conclusions.
―Rongzom Chokyi Zangpo