Heyzap is a mobile advertising platform that was acquired by Fyber for $45m in 2015. It was founded in 2008 and was located in San Francisco, California.
Topic description and Heyzap LinkedIn says the company was acquired by Fyber (recently added to this topic page as the parent organization), however, it seems that both Fyber and Heyzap were acquired by RNTS Media.
See: https://www.pocketgamer.biz/news/62530/rnts-media-buys-heyzap/ and https://blog.fyber.com/fyber-parent-company-rnts-media-acquires-heyzap/
Fyber was acquired in 2015 and Heyzap the following year. It appears that they were merged and then acquired by Digital Turbine in 2021. (see: https://ir.digitalturbine.com/news-events/press-releases/detail/610/digital-turbine-announces-completion-of-acquisition-of)