Amid the digital transformation, virtual influencer, as an emerging digital marketing innovation, is becoming a key medium for brands to connect with Generation Z consumers. This study integrates the Diffusion of Innovations Theory, Cognitive Adaptation Theory, and Information Integration Theory constructs a moderated mediation model with the image of virtual influencers (cartoon-like vs. hyper-realistic) as the independent variable, processing fluency as the mediator, and product type and advertising appeal as the moderating variables. Through two scenario experiments, the study reveals the impact mechanism of their advertising effects. The research findings are as follows: (1) hyper-realistic images significantly enhance advertising effects due to their technological credibility advantage; (2) processing fluency plays a key mediating role between the image and the effect; (3) product type and advertising appeal moderate the mediating path: functional products need to match hyper-realistic images to enhance information processing fluency, while hedonic products are more suited to cartoon-like images to evoke emotional resonance, and under emotional appeals, hyper-realistic images have a greater advantage. This study deconstructs the "technology-cognition" dual-driven path of virtual influencers as a service innovation, providing theoretical basis and strategic insights for brand digital marketing practices.