Is following da’eef hadeeths regarded as shirk?
Question

                Is it shirk to follow zaeef ahadith ? If it is then I have a question about Authentic ahadith.But Before I ask my question I would like to present the following ayat to support my question.

4:82 "Do they not ponder on The Quran ? Had it been from other Than Allah,they would surely Have found therein Much discrepancy".

 This goes to prove that any book written or given by other other Allah will have discrepancies in it.If this the case then how can we call ahadith as Authentic, if they are not Authentic then we are committing shirk.

Please clarify my confusion.
Praise be to Allah.
      It cannot be said that acting upon weak (da’eef) hadeeths 
      is regarded as shirk, because the hadeeths were narrated via chains of 
      transmission (isnaads) and the scholars researched those chains. In many 
      cases they found a man in the chain who was described as having a weak 
      memory, but that does not necessarily mean that the hadeeth is fabricated, 
      because we cannot accuse that scholar of telling lies and fabricating; but 
      he may have made a mistake in transmitting the hadeeth or attributing it 
      to someone, as happened in the case of many muhaddithoon who were 
      described as being weak in hadeeth. It is permissible to act upon weak 
      hadeeths subject to 3 conditions: 

    1.That the weakness is not so 
    severe as to make it likely that the hadeeth is fabricated.

    2.That the hadeeth comes under a 
    general principle, such as virtuous deeds.

    3.That one does not believe when 
    acting upon it that it is proven, so that he will not ascribe to the 
    Messenger of Allah (blessings and peace of Allah be upon him) something that 
    he did not do.

    With regard to the differences between hadeeths, it may be 
    due to a mistake on the part of one of the narrators; or it may be because 
    some hadeeths abrogate others as is also the case with the Book of Allah. 
    With regard to the idea that there are contradictions between the proven, 
    saheeh hadeeths, this is not correct and cannot happen, because everything 
    that has come from Allah, may He be exalted, or from His Messenger 
    (blessings and peace of Allah be upon him) is free from contradiction, 
    because Allah says (interpretation of the meaning): “Had it [the Qur’aan] 
    been from other than Allaah, they would surely, have found therein many a 
    contradiction” [al-Nisa’ 4:82]. So there are no contradicting verses in 
    the Qur'aan and there are no contradictions in the proven hadeeths of the 
    Prophet. 

    But if the contradiction involves a da’eef or weak hadeeth, 
    it does not matter, because we say that it is the mistake of one of the 
    narrators. Some of the scholars regarded it as permissible to act upon 
    da’eef hadeeth such as those that speak of virtuous deeds; i.e., these 
    reports encourage us to do some acts of virtue. But if the weak hadeeth 
    speaks of rulings, we cannot accept it. Hence Imam Ahmad (may Allah have 
    mercy on him) said: When we narrate hadeeth concerning halaal and haraam, we 
    are very strict; but when we narrate reports about acts of virtue, we are 
    more lenient, because no rulings depend on reports about acts of virtue; 
    rather they are like the virtue of fasting, jihad, prayer and so on. 

    And Allah knows best.