大方廣佛華嚴經隨疏演義鈔 9.34

9.34

The commentary's words, "Root and branch are simultaneous, from beginning to end forming one category": the root is the ekayāna, and the branches are the Hīnayāna. The three vehicles are not sequential; from the initial attainment of the Path down to nirvāṇa, these three categories of teachings operate simultaneously in parallel; hence it is said, "root and branch are simultaneous." As for "from beginning to end forming one category": if small, it is small from beginning to end; if three, it is three from beginning to end; if one, it is one from beginning to end. Hence it is said, "from beginning to end forming one category," each without conflicting teachings. Below, from "However, there are three positions...", the commentary specifically brings forth the reason.