That's a good point. When the target is a garage, it doesn't matter much, but when it's Stunts directory, unzipping the whole package there could bring problems. Pretty Garage is currently doing just that. On the other hand, if you unzip to a garage directory and then try to move the car to Stunts, it will only pick up relevant files.
In order to fix this for extracting towards Stunts directory, one alternative is to extract files one by one from the zip, but I think it'll probably be simpler and faster to unzip to a temporary directory, then move the relevant files and delete the rest.
Relevant files currently are as many of the following as they are found in the package: carXXXX.res, carXXXX.cfg, stXXXX.3sh, stXXXX.p3s, stdaXXXX.vsh, stdaXXXX.pvs, stdbXXXX.vsh and stdbXXXX.pvs, case insensitive. If Linux, these could be really many files because you can have both carpmin.p3s and Carpmin.p3s in a zip file, but this normally won't happen anyway.
In order to fix this for extracting towards Stunts directory, one alternative is to extract files one by one from the zip, but I think it'll probably be simpler and faster to unzip to a temporary directory, then move the relevant files and delete the rest.
Relevant files currently are as many of the following as they are found in the package: carXXXX.res, carXXXX.cfg, stXXXX.3sh, stXXXX.p3s, stdaXXXX.vsh, stdaXXXX.pvs, stdbXXXX.vsh and stdbXXXX.pvs, case insensitive. If Linux, these could be really many files because you can have both carpmin.p3s and Carpmin.p3s in a zip file, but this normally won't happen anyway.