schools成员没有指向任何地方，因此尝试解引用该指针会触发undefined behavior。
您需要首先为区域分配空间，然后为它指向的学校数组分配空间：

zone *zones = malloc(sizeof(zone));
zones->schools = malloc(sizeof(school)*3);

要使用分配算法，您需要尽可能使用灵活的数组成员而不是指针，因为它简化了分配和释放。

• 记住还要存储已分配对象的数量。
• 始终检查分配错误并提供错误处理。

typedef struct competition { 
    int prize_1;
    int prize_2;
    int prize_3;
} competition;
typedef struct school 
{
    int school_id;
    size_t numCompetitions;
    competition competitions[];
    
} school;
typedef struct zone 
{
    size_t numSchools;
    school *schools[];
} zone;
school *allocateSchool(size_t numCompetitions)
{
    school *sch = malloc(sizeof(*sch) + numCompetitions * sizeof(sch -> competitions[0]));
    if(sch) sch -> numCompetitions = numCompetitions;
    return sch;
}
zone *allocateZones(size_t numZones)
{
    zone *zn = malloc(sizeof(*zn) + numZones * sizeof(zn -> schools[0]));
    if(zn) zn -> numSchools = numZones;
    return zn;
}