Seven years after acquiring National Bank of New Zealand, ANZ is taking steps to introduce a simpler management structure.A single executive will now head each of the bank's retail and business banking segments.Managing director for retail Kerri Thompson, who was responsible for ANZ branches, will now also have responsibility for all of the National Bank branches.Managing director for business banking Fred Ohlsson will now have responsibility for both the ANZ and the National Bank brands.Yesterday, ANZ also announced the merger of the commercial and rural division into a single commercial  and agricultural unit. It established four regions with their own management teams: Southern, Central, Northern and Auckland.Maintaining the two brands was ANZ's priority when it acquired National Bank at the end of 2003. It dubbed the approach: one kitchen, two dining rooms.The idea was that the two brands would separately sustain ANZ's and National's combined market share, which in some segments was 40 per cent and compared with the market shares of ASB, Bank of New Zealand and Westpac.In reality, this has not proved practical to sustain. ANZ National's share in the mortgage market, for example, is now around 30 per cent. It reached around 35 per cent in 2007. For now, however, ANZ National is still suggesting the two-brand strategy remains intact.