Both effects are amplified a little bit. Personally I find it takes the worst of the alcohol and the best of the THC. So not ideal in over consumption scenarios.

If you are wanting to do it, and have never "cross buzzed" before, just take it a little slower than normal.

Weed first may also be the better move. Weed seems to hit a little harder after alcohol so tougher to anticipate how you'll handle the feelings.