Not 100% sure but that looks like damage from some sort of leaf miner. It looks similar to damage i've seen on citrus from citrus leaf miner. I've never seen it on cherimoya, but there may be a species that attacks annonas.

Thanks for the input. I've looked at the leafs and I don't really see too many insects... a few here and there, but nothing that looks like an infestation. Would you consider an "aphid" a leaf miner? I haven't seen them, but if its the same, was thinking to give it a spray with some neem oil... we had an aphid attack on a mandarina tree we have like 10-15ft away.

Not an aphid... in the case of the citrus leaf miner it's a tiny moth.

A leaf miner lays an egg on the leaf, then the larvae burrows around inside the leaf causing the damage. Then pupates, emerges from it's husk and flies off, to mate and start the cycle all over.

When I zoom into your picture it looks like there are squiggly lines inside the leaf that might be the damage left behind.

This all said, I'm not positive that is what is going on here. As I've said I have never seen leaf miner damage on a cherimoya. But this is reminiscent of such damage I've seen on other plants.

Appreciate the insight. Would you recommend Neem Oil to control leafminers?