Is Zakat obligatory on the apostate's wealth, knowing that he possesses ample funds and works in trade?

Zakat is not obligatory upon the original disbeliever, whether belligerent or a dhimmi. If he embraces Islam, he is not required to pay it for the period of his disbelief. As for the apostate, Zakat becomes obligatory upon him if he apostatizes after a full year (hawl) has passed on the nisab, and it is not waived. However, if he apostatizes before the full year has passed, it is not obligatory upon him. Zakat is also not obligatory upon him for the years of apostasy if he returns to Islam, due to the generality of Allah's saying: (Say to those who have disbelieved, if they cease, what has passed will be forgiven them) Al-Anfal/38, and the saying of the Prophet (peace be upon him): (Islam obliterates what came before it).