Grey Matter,
I suspect you neglected to read what both Yeshivish Rockstar, and I posted above.
The Tzadik has no power that is his own, all his strength is from his connection to Hashem. When a person asks a tzadik for a bracha, they aren’t asking the tzadik to fulfill their bracha, they are asking the tzadik to intercede on their behalf with Hashem, because they admit that the tzadik has a closer connection with Hashem.
How can this be? It’s explained in the works of Kavod Kedushas ADMO”R HaRaSHa”B, that every Jew has the ability, in pontetia, to reveal the essence of their soul, which is from the essential depths of G-dliness (Atmus u’Mehus B”H, as it says in kisvei HaAri Z”L, that the essence of the yechida of a Jewish neshama is “Nitzutz haBorei b’nitzutz HaNivra”) through the avodah of Torah and Mitzvos.
Practically, however, the only individuals who are successful in reaching this madreiga in avoda are tzadikim. And being that tzadikim have revealed their inner connectedness with Hashem (which all Jews share in potential), we rely on them to direct us in how to serve Hashem, and ask them for brachos in certain situations. Knowing full well, however, that the will of the tzadik is the will of Hashem, and that the tzadik is powerless to help by himself, and that it is Hashem who sends the yeshua.
And how do we know this? Because the tzadik after giving one a bracha, reminds one that the yeshua will come from Hashem, and that one must increase in their Torah and Mitzvos in order to be worthy of receiving such a hashpa, which normally they wouldn’t have been shaych to.
That’s a huge difference between the case here, and the case in the beginning of hilchos avoda zara. Here it is clear that Hashem sends the yeshua, and the tzadik himself even reminds the person, either in their Toros, or in the words of their bracha itself, that everything comes from HASHEM. By the beginning of hilchos avoda zara, the RaMBaM is describing a case where people were confused and very much believed that Hashem gave reshus to the stars to give hashpa separately and INDEPENDANTLY. Which would be kefira and A”Z.
However, to say that Hashem runs the world by using certain stars as an agent to give over a certain hashpa, is no different than saying that Hashem is mazon es hakol, by allowing us to slaughter kosher animals and eat them, and thus to derive life force and sustenance from them.
Does that mean that the cow was a separate reshus and it, separately and independently gives us life force and sustenance CH”V? NO! It means that the way that Hashem chose to create the world is by being mazon us through us eating gashmius food and that that cow was what Hashem determined would be the shliach so to speak, through which we’d derive the sustenance that Hashem intended for us in the first place.