Diversification is not a possible source of synergy when a merger occurs.
While diversification can be a strategy for reducing risk and expanding a company's business into new markets, it does not necessarily create synergies between the merged companies. Synergies are created when the combined resources, knowledge, and expertise of the merged companies add value that is greater than the sum of their individual parts.
On the other hand, economies of scale, economies of vertical integration, and combined complementary resources are possible sources of synergy when a merger occurs.