Common in English, where in some putative compounds, such as autocrat or technocrat, both members would be combining forms.
Broadacres was the ultimate landscape combining the best of the cities and the country, organicism, decentralization and usonianism.
The best progress is made by combining the practice of coöperation with the science of coöperation. They are one and inseparable to the fullest benefit. But the real way to coöperate is to coöperate.
Meaning of combining for the defined word.
Grammatically, this word "combining" is a noun, more specifically, a countable noun. It's also a verb, more specifically, a verb form.