I think there have been some gorillas who have given birth at an older age than Zaire,
Zaire is 34. Juju, one of the oldest females at Howletts was over 40 when she had her last baby in 2003. The difference being that Juju had been breeding regularly throughout her adult life.
Bristol's Salome is only one year younger than Zaire and had a similarly long interval of non-breeding as her before being sent to Bristol.