VI, reads as follows (tr. W.S. Di Piero):
Death is not evil, for it frees man from all ills and takes away his desires along with desire's rewards. Old age is the supreme evil, for it deprives man of all pleasures while allowing his appetites to remain, and it brings with it every possible sorrow. Yet men fear death and desire old age.
I don't know if it's ever been noticed, but this passage in Leopardi recalls a poem by Crates the Theban, an ancient Greek Cynic philosopher, quoted by Stobaeus 115.9:
You cast my old age in my teeth, as a great evil.
Death is the penalty for him who does not reach old age.
We all desire old age. But when it arrives,
We are distressed. So ungrateful are we by nature.
Leopardi mentions Crates twice in his Zibaldone