Guevara was actually very much involved and interested in economics and in managing the Cuban economy until early 1965, but was unable to convince his colleagues that his alternative approach was better than what was practised in Eastern Europe, which he correctly predicted would lead back to capitalism! He was apparently pushed out of the government responsibilities, and so he left for Africa, possibly not particularly enthusiastically?
On
this page that starts with a nice photo of Che on a tractor during his first visit to Czechoslovakia
as a Cuban minister,
an "Espresso Stalinist" seems to have a somewhat complementary view - that Che's approach to economy was in line with the late Stalinist economy (which especially Stalin's adherents consider the best socialist economic system of all that were tried during the existence of the USSR).
Those Zetor tractors were familiar machines of my childhood in the Czech countryside.
At that time I was in about grade six, and most probably had not yet had any idea about the existence of Che.
Later in 1966 Che spent about half a year in Czechoslovakia incognito (supposedly on a false Uruguayan passport and without the knowledge of the Czechoslovak government!), recuperating there between his involvements in Africa and Bolivia. Czech radio aired two pieces on this stay, in English, in 2010 and 2016, apparently based on the information from declassified archives.
Besides putting his health in order, he most probably used this time also, or mostly, to complete his voluminous
Notes on the political economy (in Spanish), according to a passage in the thesis of Helen Yaffe (see above).
My note: Instead of loosing his time (and ultimately life) in places that were not yet ripe for
revolution, would it not have been better for him to spend all the time after 1964 on the research
in the political economy of socialism? This came to my mind, because some contemporary Russian Marxists analyzing
the Soviet experience think that the fact that there was no Theory of Building of Socialism (nobody of those who carried out the revolution had time to write such theory) contributed substantially to the demise of the USSR. (Some also think that the Cuban revolution at least invigorated and prolonged the duration of socialism in USSR by a a minimum of 20 years.)
Lastly, somewhat related, interesting read: Reluctant Czechoslovak support of revolutionary violence since the 2nd half of 1960s, because of the fear of damage to their foreign trade. Che Guevara thought that it was wrong to trade with the capitalist countries at all, that all socialist countries should trade only among themselves. But apparently neither the Cuban leadership had made full effort toward this goal, as a decade into its revolution, Cuba was still disorganised, and its allegiance to socialism had not overcome its commitment to the US dollar. This last article is based on information from declassified Soviet archives. It's an interesting read from the beginning to the end. It illustrates how difficult it was to try to build socialism within the international financial system set up by the capitalists, in only a small number of countries. Otherwise it shows that the Soviet officials were doing their best to accommodate the needs of Cuba, and that they have not used against Cuba the same kind of bullying/sanctions that USA often applies to push around their allies/satellites.