hmmm... why? Note that Christianity holds that God is One, Jesus being part of a Trinity. Of course, I agree that non-Christians would not be able to accept this, but I mean it's not impossible from a strictly logical point of view to be Jewish and accept a Triune God -- still monotheistic.
however, I repeat, it is your choice to believe what you wish -- God be with you.
Except the Trinity goes against the strict monotheism of Judaism, and it’s one of the reasons why Jews don’t accept Jesus.