Obtained with commands:
  sed -i 's/val_of_Z_is_some/val_of_Z_is_Some/g' **/*.v
  sed -i 's/val_to_of_int/val_to_of_Z/g' **/*.v

This was done using the following sed commands (with ZSH ** pattern):
> sed -i 's/val_of_int/val_of_Z/g' **/*.v
> sed -i 's/val_to_int/val_to_Z/g' **/*.v