PowerShell, 92 bytes

I think there's definitely some room for optimization here; A lot of the bytes are just there to handle the cases with the leading "\d "

$t=1;-split$args|%{$t*=$_-replace'\(','+('-creplace'[A-Z][a-z]*','+1'-replace'_','*'|iex};$t

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Honorary Mention, PowerShell, 99 bytes

This was my first solution, and I really liked it. Including it here because I think it's fun.

$o="'-creplace'";"'$args$o^','`$n=$o=\d','`$0;`$n*=$o\(','+($o[A-Z][a-z]*','+1$o`_','*'"|iex|iex;$n

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