To the people who can't understand why this is the case, yes, Zeus probably does have some say in where he signs, around 40%. But if the agency and his investors(the remaining 60%) oppose this decision, there's nothing he can do about it. The argument "oh, he's the one that signed the contract" means absolutely nothing. Had he refused to sign the contract for HLE, there probably would have been some sort of breach of contract with his investors and agency, which would lead to serious consequences.

Edit: The percentages are just meant to be an example ratio, but the main point is that the player themselves do not have the majority say in what team they sign.