Where did you get your zip file from? I know at least 2 different cores for STM32F1.
Usually it is the best to get a .json install path, copy it as additional Boards Manager URL in preferences and install the core by means of the boards manager. If there are already other URL's append it separated by a comma.
For Roger Clarks core: http://dan.drown.org/stm32duino/package_STM32duino_index.json
for the STM core: https://github.com/stm32duino/BoardManagerFiles/raw/main/package_stmicroelectronics_index.json
My favourite for STM32F1 is the core of Roger Clark, but the STM core supports more ( I think nearly all ) STM32 devices.