Since other abilities like Vader's, JKR's and EP's abilities double-dip for allies with multiple relevant tags, I would be very surprised if 5's zeta doesn't.
No, only 15%. When the effect is doubled (JKR lead, Vader unique) the wording says 'for each ally' of a certain faction, and they are tied with 'and'.
'Or' means when either of the conditions are fulfilled, doesn't double up when both are met.
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... But no, I didn't test and verify it.
'Or' means when either of the conditions are fulfilled, doesn't double up when both are met.