if you think of the offensive and defensive efficiency as percentage of points scored per each possession, then to incorporate an opponents efficiency factor into a team's expectation you would multiply the teams respective efficiency numbers by the average pace
For example
Team A: Pace 95.1
Team B: Pace 90.1
Expected Pace = (95.1+90.1)/2 = 92.6
Team A: OE = 1.01
Team B: DE = .91
Expected Team A points = 1.01*.91*92.6 = 85.11
Team A: DE = .85
Team B: OE = .99
Expected Team B points = .85*.99*.92.6 = 77.92
Final score
Team A: 85.11
Team B: 77.92
Here is a spreadsheet I made about 3-4 years ago, one for NBA one for college with the formulas already filled in, you just need to enter the pace and efficiency numbers in the appropriate cells (for NBA I use
82games.com for stats, NCAAB I use kenpom and bbstate)
THe files are in excel. Make sure you DO NOT fill down the formulas for they are inconsistent from one cell to the next. Each cell corresponds to its preceding crossover, so if you need to add cells do it manually. I have pre-filled a ton though so it should be plenty to get you started