Certified GKH Gardening Expert
You can remove these if you want or leave them. Either way is fine and will not cause any issues with the tree. If you choose to take these pods off, these articles should help with pruning: https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/pruning-crepe-myrtle-trees.htm
I live in zone 9.
Seed pods may be removed any time. I just leave mine on since my trees are so large.