In view of a growing family, he converted from a structurally oriented field-geologist to a more sedentary, stratigraphic trap hunting subsurface-geologist and chalked-up his first natural gas discoveries in the Alberta down-dip reef belt.

After guiding an airborne excursion through the Cordillera during the 1967 Devonian Symposium of Calgary, his guidebook, summarizing “The Development of Sedimentary Basins in Western and Arctic Canada”, was published by the Alberta Society of Petroleum Geologists in 1969.

As the North Sea success story unfolded, Shell and its partners were rewarded with numerous important oil and gas discoveries, including the giant Brent, Statfjord, and Troll fields.

In the same line, the American Association of Petroleum Geologists invited Ziegler to tour the United States and Canada in 1986-1987 as distinguished lecturer, speaking on the Evolution of the Arctic-North Atlantic and Western Tethys.

In short succession he published with Shell's support in late 1988 the AAPG Memoir 43, entitled “Evolution of the Arctic-North Atlantic and Western Tethys”, in 1989 a volume published by the Royal Geological and Mining Society of the Netherlands on “Evolution of Laurussia - A Study in Late Palaeozoic Plate Tectonics” and in 1990 for Shell's 100 years of Exploration Jubilee the 2nd edition of his “Geological Atlas of Western and Central Europe”.

On the occasion of his 80th birthday the Swiss Geological Society honoured Ziegler with a symposium on the theme “Deep Earth - from Crust to Core”, held in Lugano on 23 November 2008.