Ideally when it comes to taming wild animals such as zebras, wolves, lions or orangutans and so-on - it is best to start when they are newborn or if they are still infants, which is generally when their psyche is still rather malleable. That said, it is still a rather delicate process and can endanger or harm both the trainer and the animal if not careful; especially if it is a type of animal that is skittish, nervous, uncalm and otherwise unsuited to enclosed pens (which is usually a prerequisite for domestication). Asian Elephants for example can be tamed unlike their African cousins yet the are only
partially domesticable as their mating habits cannot be behaviourally modified (well not yet that is...( ͡° ͜ʖ ͡°)...). So we're probably still not going to see any commercially viable "elephant stud farms" in the near future

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Domesticated horses those creatures are usually at the mercy of selective breeding, whereas wild and feral horses tend to "coalesce" in either
harems or
bachelor herds. As a rule, and depending on an species psychology, it is perfectly possible to
tame wild animals like wolves, zebras and elephants to be able to tolerate people, human handling and human environs. However to successfully and
fully domesticate such creatures, one would have to turn a naturally wild, skittish creature such as a Zebra into one that is naturally calm and docile which is a process that takes centuries to do (same as with early cats, dogs & horses) - and longer still if one seeks to add or refine certain traits into a breed such as better endurance, stamina, fur colour, intelligence, thicker skeleton & musculature and so-on.