Zumbador literally translates to "hummingbird" or "buzzer." It's an interesting and somewhat uncommon word to find in song lyrics, making it memorable.
In this song, the artist uses zumbador metaphorically to describe someone who flits from flower to flower, implying a person who is unfaithful or a playboy. The singer denies being this zumbador, assuring his love that she is the only one for him.
Dalvin La Melodia kicks off "Mi Reina" by confronting nasty gossip. His partner is in tears because someone told her he is a player: "Sé que te han contado que soy como el zumbador / Que vive picando de las flores la mejor" ("I know they told you I am like the hummingbird / who goes around pecking the best from the flowers"). Calling a guy a zumbador (hummingbird) flitting from flower to flower is a classic tropical idiom for someone who flirts with everyone and never settles down. Dalvin begs her not to believe it. To him, she brought light into his dark days, and he insists he literally forgets how to breathe if she is gone: "Sin ti no sé respirar" ("Without you, I don't know how to breathe"). It is completely over the top, but bachata thrives on high-stakes drama.
He calls her "mi reina" ("my queen") and "mi linda princesa" ("my pretty princess"), reminding her that she was there during his absolute lowest points. He credits her as his "vaso de agua cuando más tenía sed" ("glass of water when I was most thirsty") and the one who held him when he was alone. Midway through, he gives shout-outs to his bandmates Mickey and Mayimbito to keep the rhythm driving. He argues that he cannot cheat because he is hooked; losing her would mean he completely loses his mind ("voy a perder el control"). It is pure romantic pleading, meant to clear his name and soothe her doubts.