وَلَدَ اللَّهُ
...
that they say: "Allah has begotten."
meaning, that offspring have been born to Him.
...
وَإِنَّهُمْ لَكَاذِبُونَ
And verily, they are liars!
Allah mentions three of the things;
they said about the angels, which formed the utmost disbelief and falsehood.
They said that they were the daughters of Allah and that Allah had offspring -- exalted and sanctified be He above that.
Then they made these offspring female, then they worshipped them instead of Allah, exalted and sanctified be He -- any of which on its own would be sufficient to condemn them to spend eternity in Hell.
Then Allah says, denouncing them:
أَصْطَفَى الْبَنَاتِ عَلَى الْبَنِينَ