Could you explain what the conflict of interest is? Only me and @hanh have contributed code to the BTCPayServer Zcash plugin. In any case, I don’t feel that simply contributing code to a project would constitute a conflict of interest if it is unpaid and there isn’t some commercial motive.
I feel that @hanh’s input into the discussion would be valuable (at least when it comes to technical expertise, this could be a separate comment in the form of a forum post though); however yes, there would likely be a conflict of interest when it comes to a vote due to his work on zcash-walletd.