Split routine into two-a-day workout schedule

Question

I have been doing a 6 day/week push-pull-legs routine. I have one 90 minute gym session on each of those days. Recently my schedule has changed and I can only manage two 45 min gym sessions for 6 days/week. I would like to know how to split my routine for such a schedule. Also, if my existing routine is not amenable to splitting into two-a-day workouts, I would be grateful to know what exercises I should substitute for existing ones.

For those who are so kind as to help me with this question, I would be grateful if you could explain your reasoning behind splitting my program in a particular way. I am confused about this topic and would like to go into this schedule prepared. For example, I am wondering if I break up a push routine into two sessions on the same day, wouldn't I be over training certain muscles? And if I don't break it up like that (instead opting to, say, do push exercises in the AM and pull in the PM), how to I make sure I get the needed 2 to 3 days rest between hitting a given muscle group? By the way, my goal is hypertrophy.

Here's is my existing training schedule (adapted from a Jeff Nippard program):

Day 1 (push)

1. Wide grip bench press
2. Seated overhead dumbbell press
3. Low-to-high cable crossover
4. Dip
5. EZ bar skull crusher
6. Lateral raise

Day 2 (pull)

1. Lat cable pulldown
2. Pullups
3. One-arm dumbbell row
4. Cable pulldown row (torso leaned back)
5. Cable face pull
6. Reverse EZ bar (superset part 1)
7. Supinated EZ bar (superset part 2)
8. Dumbbell preacher curl

Day 3 (legs)

1. Barbell squat
2. Dumbbell deadlift
3. Cable pull through
4. Dumbbell walking lunge
5. Cable leg extension
6. Seated cable curl
7. Cable standing calf raise

Day 4 (push)

1. Close grip bench press
2. Overhead shoulder press
3. Incline dumbbell
4. Single arm cable fly
5. Cable lateral raise
6. Triceps cable pushdown

Day 5 (pull)

1. Neutral grip cable pulldown
2. Cable seated row, arms out (superset part 1)
3. Cable seated row (superset part 2)
4. Kneeling cable pullover
5. Barbell shrug
6. Reverse cable fly
7. Single-arm cable curl
8. Hammer curl

Day 6 (legs)

1. Dumbbell deadlift
2. Goblet squat
3. Dumbbell stepup
4. Cable leg extension
5. Swiss ball leg curl
6. Seated calf raise

Day 7 (rest)