Not a good idea: it's only been three weeks since you submitted the revision, and if the editor is inviting reviewers, that's too short a time for the reviewers to finish their reviews.
It's unfortunate that you really, really need a decision now, but if you press for one, you put the editor in a bind. They effectively have to make a decision now without the reviews. If they aren't an expert on the topic itself, it would come down to this question: would you rather publish a potentially flawed paper, or reject a potentially good one? That's not an easy question and different people will reach different answers; however, if you believe your paper is good and will pass the second round of review, there's no need to risk the editor falling in the latter camp.
tl; dr: wait however long it took for the reviewers to finish the reviews in the first round of review before asking for a decision.