Works great for a pre-contest thing.... big bodypart for the first workout and the smaller one done in the evening , usually with cardio.....
Now keep in mind if you choose to do the 2-a-day workout, it's usually a day-killer....
You need to get up and get the fuel in and timed for a good workout.....once ready, give 'er.... but remember, you will be back in the gym in 6-8 hours....
Go home, eat and get a meal prepped for post nap.... eat, then nap.... as much as you can ... this is how you will recover for the next session...
Eat upon waking or as soon as you can.... try and eat once more before going back in the evening...... this is when a lot of folks use stims of some type....
Hit the second session.... just know your intensity may be down a bit and should be.... this is why most splits like this are done big part/small part.... your CNS will take a beating if you try and go balls-to-the-wall 2x in one day.... my best advice is keep the intensity at about an 8-9.... with 11 being the type of set with drops, rest pause or any other technique to extend the set ..., you'll want volume here, not PR's..... also why its best to train push and pull muscles together like this..... i.e chest and delts in the morning, or just chest, then tris ( or delts and tris) in the evening.... so it's not like these are 2 marathon sessions... you just split the workload out over a day instead of a couple of hours.... also good if you have lagging body parts you'd like to bring up