Is it incumbent upon one who committed Shirk, then repented, then committed Kufr – not Shirk – then repented, to repent again from the first Shirk, for fear that his previous repentance might have been nullified?

Shirk (associating partners with Allah) and disbelief invalidate deeds, as stated in the Almighty's verses: "If you associate others with Allah, surely all your deeds will be annulled" and "And whoever amongst you turns back from his religion and dies as a disbeliever, then their deeds will be annulled." Many scholars are of the view that invalidation of deeds (hubut) only occurs if the apostate dies upon disbelief. However, if he repents and returns to Islam and dies as a Muslim, his previous deeds are not invalidated.