Malu (born 2003) is the son of Santan/Maimunah. Others may know him as Menyaru, due to Melbourne Zoo’s double name thing.
The reproductive age females at Perth Zoo could be suitable mates for Malu.
The decision to export the 1.2 Sumatran orangutan to Sydney Zoo (and retain the hybrids) isn’t as strange as it sounds. Santan and Maimunah are getting on in their years and probably won’t be bred from again. Melbourne Zoo are very proud of Kiani - being one their famous orangutan twins (which are still mentioned in the media from time to time). They probably had no objection to retaining her; while forming a new breeding pair with Malu and a new female.
I think Pulang (born 1993) is the most likely export out of Perth Zoo, given that her mate (Hsing Hsing) is now deceased. I think Perth Zoo will retain Sekara (1990) and Teliti (2009) for breeding with Dinar (1987); while Pulang’s daughter, Lestari (2012) could go either way. If Pulang is sent to Melbourne, she may remain at Perth as a third breeding female; if Pulang goes to Auckland Zoo, they’d have space to take mother and daughter.
There’s more info on the Perth Zoo colony (including how they’re related) here:
Orangutans [Perth Zoo]