In plain words
‘Gurudevo maheśvaraḥ’: who is Maheśvara? That is, Maheśvara is He who governs every living being in this world. What has this Īśvara ordained? He is the one who gives the right teachings on how each one must conduct himself, on what days, at what times and in what places. He is the one who rules this world well. Sunrise and sunset are a law! The seasons are a law! Rain is a law! Night and day are a law! Everything is law! So all things, to the very letter, without fail, are made to keep discipline: Īśvara is the one who gave the world that law. So they said that all three of these are Gurus.
God is one! Forms and names are different
The Guru is not merely one who teaches learning. The one who is endowed with every power is the Guru. The one who knows all is the Guru. The one who pervades all is the Guru. The one who holds everything in His hand is the Guru. What does Viṣṇu mean? One with four hands holding the four, the conch, the discus, the mace and the lotus? In one hand the conch, in one hand the discus, in one hand the mace, in the other the lotus: what is the inner meaning of this? The conch means sound. It is in God's hand. The discus is the wheel of time. The mace means strength. The lotus is the lotus of the heart. Everyone's heart is right in God's hand. So in this way God is the one who has every power! With the conch, discus, mace and lotus in view, they have gone on teaching the world that this is Viṣṇu. But here they said ‘Viṣṇu’; there they said ‘Īśvara’. People think, ‘Īśvara and Viṣṇu cannot get along at all!’ For them not to get along, they would have to be two; the two of them are one! There are some who worship Śiva and Keśava. They are narrow minds; they cannot get along with one another. One says, ‘I am a Vaiṣṇava.’ Another says, ‘I am a Śaiva.’ All this is nothing but narrow feeling! They fight among themselves, but what exists is one!