Sankaracarya's Vivekachudamani 471

अनिरूप्य स्वरूपं यन्मनोवाचामगोचरम् ।

एकमेवाद्वयं ब्रह्म नेह नानास्ति किंचन ॥

anirūpya svarūpaṃ yanmanovācāmagocaram |

ekamevādvayaṃ brahma neha nānāsti kiṃcana ||

(Sankaracarya's Vivekachudamani 471)

The Real Nature which is incomprehensible, which is beyond mind and speech and non-dual, there is only the Brahman; in It there is no duality whatsoever.

We as a conditioned soul and jivatma not easy to understand all the creation of the Lord. It's beyond our intelligence and imagination. We cannot come to a conclusion about the Supreme Lord's creation. There is nothing like his creation in all three worlds. Therefore He is the Supreme Lord. He is an unchangeable Lord always and forever.