The process in which zygospores are formed. Zygospores are characteristic of the zygomycete fungi (phylum Zygomycota) thick-walled and darkly colored, and usually heavily ornamented as well, with many spines or ridges. It is formed between two specialized organs called suspensors, which are themselves usually heavily ornamented, one from each mating partner. The zygospore forms between them and then breaks away.