By synergy if you mean that you cannot do it alone, and God has to be with you or the universe should approve of you or whatever, then the Supreme Buddha’s Dhamma is not synergetic. The formlessness of the God, Yehovah and Allah has resulted in banning idol worshipping and making statues or drawing pictures of the "unmanifested" being forbidden. There are these do’s and don’ts in other aspects too of these religions.
That said in Buddhism, one needs the assistance of fellow Dhamma-farers who are fully established in the path, and the Devas, (at least up until you yourself is fully established in the path as a stream entrant) if one is to succeed in this path.
If the continuance of the round of rebirths occurs due to Dependent Origination, the latter must cease for the round of rebirths to cease occurring. The way to make that happen is to follow the Noble Eight-fold Path. To fulfil that process, one needs to association of noble friends, hearing the Doctrine and keep company with righteous people. He would also need a rebirth conducive to fulfil the process of following the Noble Eightfold Path. Now, that is where merit plays its part.
A rebirth in worlds of the Brahmas and Devas becomes a very helpful asset to one who searches for the goal of Nibbana. Such rebirths are the results of merits. So we must understand the true worth of merit. Those who spend the time arguing "We do not need merit but only wholesome deeds" unfortunately may end up getting neither.
Whoever is in the Noble Eight Fold Path – the road less travelled, need the company of Noble Friends who would encourage you in this path. When Ven. Ananda told The Buddha that 50% of the path depends on the association of Noble Friends, The Buddha corrected him, saying that it is depended 100% in the association of Noble Friends.
Sadly in the present day and age there are many so-called-Buddhists that bear misguided and false views harming themselves and many around them. In Sri Lanka specially, there are many who carry false beliefs while taking refuge in auspicious times according to asterism, auspicious signs, horoscopes, planetary objects, and the twelve houses of astrology. None of these have anything to do with Buddha’s teachings.
We live in an unfortunate time where the Asura Forces are far greater and stronger. One would only make one’s refuge in the Triple Gem impure by believing in horoscopes, following auspicious times etc. etc... Tell me how many of us ‘Buddhists’ have made the Sutta & Vinaya Pitaka (the Doctrine) of the Buddha, their teacher? It’s only a handful. We may say that we seek the blessings of the Triple Gem to protect and guide us, but what we go behind and look up to are the politics, the horoscopes, the auspicious times, the Asuras that we call ‘Gods’, and other ‘a’dhammas. So to overcome these we need the assistance of Davas who are well established in this path. In this way, the Supreme Buddha’s Dhamma is synergetic.
Many Buddhists in the present day may believe that beings in the worlds of Devas cannot accumulate merits. This view is contrary to the discourses of the Buddha. In the Doctrine, there is a meditation called the 'Contemplation of Devas'. In it the Buddha spoke about The World of the Four, The World of the Thirty Three, Yama, Tusita, Nimmanarati, and Paramimmita Vasavarti. These are all Deva Worlds.
A disciple who has developed the powers of a Noble learner such as faith, virtue, learning, liberality and wisdom, has the qualities to receive a rebirth in those Deva Worlds. Such a disciple with the powers of a Noble learner could contemplate: "Devas too have noble qualities that I possess. After my death in this world, I can receive rebirth among the Devas". Thus the disciple with the powers of a Noble learner does the meditation called 'Contemplation of the Devas.'
If one cannot lead a life of virtue and Dhamma in the worlds of Devas, The Buddha would not have taught His disciples how to meditate on the 'Contemplation of the Devas'. Another thing we know is that when the Buddha preached 'The Motion of the Wheel of Truth' (Dhamma Cakka Pavattana Sutta) only one person in the world of human beings reached fruition of the path, while Devas in twenty two worlds of Devas reached fruition of the path.
In Samyukta Nikaya there are discourses called Devata Samyukta and Devaduta Samyukta. When these discourses were spoken by the Buddha, there were many beings from the world of Devas who reached the fruition of the Path. Sakkapanha Sutta in Digha Nikaya (collection of long discourses) shows that Sakra, the Lord of the Deva world of the Thirty Three had reached fruition of the Path.