It's absolutely not going to work. There is simply no possibility.
There's obviously the fact that your work would absolutely suffer - how will you sit on zoom calls with a crying baby? How will you work at a laptop if your baby is one of the many who won't nap unless being cuddled or walked? How will you make up for the time spent changing nappies, feeding your baby etc when you'll also be up all through the night and needing to rest at some point yourself?
But more importantly, this would be so bad for your baby. Babies thrive on the input they get from their parents - the playing, the being talked to, the stories, the cuddles etc. A baby who isn't getting these things because their parent is working will not thrive. You would be severely compromising your baby's start in life, and you can't make that time back up later.
Looking after a baby is a full time job. There's simply no way to do another full time job alongside it. It would be so very bad for your baby for you to consider this.
You need to find another option. Since your workload is so light could you ask your employer if there is scope for you working 3 days rather than 5? They might not be willing to pay you full time for that (and you might not want to illustrate to them that you don't actually have enough work for a full time job) but since they're apparently happy for you to try to work and look after a baby, they might be flexible. Then you would only need to find a solution for 2 days, since your mum can cover one.
Can your husband work compressed hours so he has one day a week off? Can he go part time for a while? Can he take a sabbatical or period of leave? Does his work have a shared parental leave policy? Sometimes they can be an excellent way of getting more paid months of leave between you than you would get on maternity alone.
Can your mum he persuaded to do an extra day? Any other family who would help?
Can you find another job with part time hours for better pay?
Can you take out a loan to pay for childcare? Sell anything?
Can you reduce your living expenses so that you can stop working?
I do basically think you're being profoundly naive here, and considering decisions that won't work for you, your baby or your employer. You have to wise up a hit before the baby arrives, and that might involve some difficult decisions. It really sounds like you might have to rearrange quite a lot of your life to make this work.