The upper/lower 4 day/week split is one of the best, time tested workout splits there is, and 4 days a week is doable for most guys.
For this particular workout routine, I've tweaked the standard split and differentiated the two workouts, so they are not exactly the same on M/T and T/F, and slightly different focuses.
(All working sets done to failure. Focus on form and full range of motion. 1 second up/2 seconds down rep cadence.)
Monday - Lower Body (Glute/Hamstring/Posterior Chain dominant)
Leg Press (wide stance) - 3 sets x 8-12 reps
Hip Thrust - 2 sets x 8-12 reps
Romanian Deadlift - 2 sets x 10-15 reps
Leg Curl (seated or lying) - 2 sets x 10-15 reps
Standing Calf Raises - 2 sets x 15-12 reps
Ab Crunches - 3 sets x 10-20 reps
20-30 minutes cardio - Low Intensity (Incline Walk or Stationary Bike)
Tuesday - Upper Body (Back/Chest Dominant)
Dumbbell Bench Press - 2 sets x 8-12 reps
Incline Bench Press (Machine or Dumbbells) - 2 sets x 8-12 reps
Lat Pulldown (Wider Grip) - 2 sets x 8-12 reps
Machine Row - 2 sets x 8-12 reps
Seated Dumbbell Shoulder Press - 2 sets x 8-12 reps
Bicep Curl (Straight Bar or Dumbbell) - 2 sets x 6-10 reps
Seated Overhead Dumbbell Tricep Extension - 2 sets x 8-12 reps
20-30 min Cardio - Moderate Intensity (Incline Walk or Stair Climber)
Thursday - Lower Body (Quad Dominant)
Leg Extensions - 2 sets x 15-18 reps
Leg Press (Narrow Stance) - 2 sets x 8-12 reps
Hack Squat - 2 sets x 8-12 reps
Standing Calf Raise (Or Donkey Calf Raises) - 2 sets x 15-20 reps
Machine or Cable Crunches - 3 sets x 10-12 reps
20-30 min Cardio - Low Intensity (Incline Walk or Stationary Bike)
Friday - Upper Body (Shoulder/Bicep/Tricep Dominant)
Lateral Raises w/Dumbbells - 2 sets x 12-15 reps
Machine Shoulder Press - 2 sets x 8-12 reps
Rear Delt Flys (Machine or Dumbbells) - 2 sets x 10-12 reps
Tricep Pushdowns - 3 sets x 8-12 reps
Bicep Machine Curls - 3 sets x 8-12 reps
20-30 min Cardio - Moderate Intensity (Incline Walk or Stair Climber)