The Buddha is not a God but Inspiration for Buddhahood
Regarding Buddhism, the Buddha is not a god, yet Buddha-essence is like a gift given to everyone on birth. She who accepts this wisdom shall uncover the Buddha within.
It takes listening carefully to the Buddha's story to awaken this essence, and every Buddhist who keeps his own story a secret is turning the Buddha away. For everyone is free to become a Buddha, yet few of them are ready.
For they who are not ready have yet to understand what the Buddha means to them.
For me, the Buddha means peaceful bliss and the aspiration to be of service to anyone seeking the calm awakening that meditation provides.
If this is a turn-off to atheists, then that's their karma for confusing Mahayana Buddhism with monotheism.
In my opinion Zen Buddhists are closet atheists. They achieve their Buddha-hood by self-power.
Because self-power sometimes leads to ego delusion, this may explain why Zen Buddhists do not think much of chanting a mantra or Buddha Remembrance (repeating the Nembutsu (Nian-fo) until one reaches samadhi).
Yet the fathers of Zen and the Chinese Ch'an master before them praised the Nian-fo practice since it quickly hastens the practitioner's path to Buddha-hood due to intent to be reborn in the Pure Land of Ultimate Bliss.
Zen masters do not understand this as their self-power path blinds them, and thus prevents them from considering the easy way to Buddha-hood.
I on the other hand find zazen practice to only contribute to hemorrhoids rather than satori. YMMV
For Nian-fo practice quickly aids the mind-stream in achieving Buddha-hood, as the Pure Land that in which the practitioner believes he will be reborn is surely the optimal place to swiftly achieve Buddha-hood.
Any Zen master who doubts this is thus blinded by the ego delusion arising from his flavor of self-power.
Indeed, it is the Other-power of Nian-fo that helps the Nembutsu practitioner to achieve what the Theravada and Zen practitioners cannot: rebirth in a Pure Land that helps all Buddhists who have faith in Other-power to quickly help them achieve Nirvana and ultimately, Buddha-hood.
For the Pure Land is conducive to achieve Buddha-hood.
Thus it is by Buddha Remembrance that Nembutsu practitioners become Buddha.