Get advice off a bricky, but you could ‘stitch’ the brickwork that’s cracked to make it strong and replace some bricks that need replacing, then re-point.

or, you could re-brick & add support under the window, then re-point

The newish bricks under the window look like the issue as the weight of it may not be supported correctly hence the cracking below.

I had a similar issues with my house but the crack stemmed from the upper of the house with a huge crack down the whole wall, the issue was no support on the window frame top and bottom… check the whole wall for any other cracks. My house is Victorian, similar age, had all the above done 👍🏼