product of 2 stoch processes driven by same BM

Given
dXt := dBt
dYt := 5dBt
X0 = Y0 = 0
Let Zt :=XtYt  so dZ = X dY + Y dX + dX dY = (10Bt ) dBt + 5 dt  
So we get a positive drift from 2 driftless processes! Paradox?
A: Well, when dB is negative, dZ would get a positive drift (product of 2 negative values). dZ drift is always positive i.e. always trending up, always biased.
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