Credit Miles to UA and Then Another?

Greetings to your day,

Starting in NYC/PHL, I'm looking at (*A-only) flights to SE Asia, trying to route them through various US cities. I'd like to try and take advantage of my UA*G, then start crediting miles to another *A carrier (as the TPAC decidedly wouldn't be with UA).

Is it possible to do this with same-day TPAC connections, or only if they are split up by days, or do they have to be separate itineraries altogether?

Thanks for your help,
BmB