What two masters?
The written law of the fathers (corrupted mankind) law or doctrines of men as to what they must as a law call Sacred Tradition of the fathers. They take that written authority and make the authority of sola scriptura without effect. There losing the DIVINE power of God by which we can beleive as he works in us to make it possible .
Placing the what they Sacred Tradition of men over and above God's tradition. Following that pattern in order to make sola scriptura without effect. , Same kind of law of the fathers found with the Pharisees with Sadaucesss .two sect that had no faith exclusively coming from scripture
Sacred Tradition #80 the fathers bock of the law.
Sacred Tradition
and Sacred Scripture, then, are bound closely together, and communicate one with the other. For both of them, flowing out from the same divine well-spring, come together in some fashion to form one thing, and move towards the same goal."
There is a great parable in regard to mankind trying to serve two masters in Luke 14 that shows that kind of Catholic worldly mindset . Looking for alternative source of faith by what the eyes see. No faith need that comes by hearing God exclusively .
(No man can serve two teaching Masters)