The physiological, developmental and morphological changes that occur in the symbiont encysted zoospore, which is on or near its host organism and germinates by developing a germ tube that may penetrate the host directly or indirectly through an appresorium. An encysted zoospore is a zoospore which has shed its flagellum and whose membrane has fused to form a walled cyst. The host is defined as the larger of the organisms involved in a symbiotic interaction.