What is a better exercise gym routine for better results you think?

I go the gym four times a week and first do 4 to 5 miles of Cardio walking and running on treadmill then lift weights but I be too tired for lifting weights and feel I'm not reaching my potential due to fatigue.

I'm think of doing 2 days of Cardio only and 2 of lifting weights only but that will cut my 4 days of Cardio off and I don't want that neither.

What is a better exercise gym routine for better results you think?
What is a better exercise gym routine for better results you think?
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