I read a version of the Isha Upanisad / Isopanishad with a strongly theistic interpretation, which didn’t suit me. Looking for alternatives, I found various translations of the Isha Upanishad, among them a commentary from the website: http://www.yoga-age.com/upanishads/isha.html

When I posted them on another forum, someone told me this post may create a "debate". I'm not into causing trouble but I'd really have some answers. My questions deal with possible contradictions of the Bhagavad Gita and the Isha Upanishad.

Here are my questions:

On Knowledge and Ignorance
Isha-Upanishad 9
They enter into blind darkness who worship Avidya (ignorance and delusion); they fall, as it were, into greater darkness who worship Vidya (knowledge). (Aurobindo translation)
Then why is said in the Bhagavad Gita:
4.10. Delivered from liking and fear and wrath, full of me, taking refuge in me, many purified by austerity of knowledge have arrived at my nature of being (madbhavam, the divine nature of the Purushottama).

On the Unmanifested and the manifest

Isha-Upanishad 12
They fall into blind darkness who worship the Unmanifested and they fall into greater darkness who worship the manifested.
The Bhagavad Gita says:

BG 12.3-4. But those who seek after the indefinable unmanifest Immutable omnipresent, unthinkable, self-poised, immobile, constant, they also by restraining all their senses, by the equality of their understanding and by their seeing of one self in all things and by their tranquil benignancy of silent will for the good of all existences, arrive to Me.

12.5. The difficulty of those who devote themselves to the search of the unmanifest Brahman is greater; it is a thing to which embodied souls can only arrive by a constant mortification, a suffering of all the repressed members, a stern difficulty and anguish of the nature.
I assume Krishna is not the manifest, as the BG says:
7. 24. Petty minds think of Me, the unmanifest, as being limited by manifestation, because they know not my supreme nature of being, imperishable, most perfect.
7. 25. Nor am I revealed to all, enveloped in My Yoga-maya; this bewildered world knows Me not, the unborn, the imperishable.

So I assume the manifest is materialism?

Excuse me if there are errors in my opinion, I want to learn. Thanks for your answers.