[Brief hijack]
You seem to be postulating a far wider philosophical gap between Hinduism and Buddhism than I think exists. For instance, the ‘atman’ aspect of Hinduism exists to reconcile with the ‘Brahman’. Which is to say your true unchanging self is the same as everything else(which to me really says it doesn’t exist). And there are strains of Buddhist thought that also talk about ‘atman’. On the (very slightly) broader question of whether you can be both Hindu and Buddhist at the same time…I don’t know, but I think it’s quite possible.
[/Brief hijack]