Your time frames off a bit
As soon as Broly feels his opponent build upchakra and start to release it in the ground he merges with the ground and comes up just behind his opponent undetected while leaving a shadow clone of himself where he used to be.
(Bunshin No Jutsu) - Clone Technique
Rank:E
Type:Supplementary
Range:Short
Chakra Cost:5
Damage Points:N/A
Description:A clone made of the user that can move but(cannot use any jutsu)This clone is merely an illusionary projection of the user.
Note:The clone jutsu can be made with different elements and is a D-Rank jutsu under its own element(Mizu/Water Tsuchi/Earth Sumi/Ink)
(Doton: Iwagakure no Jutsu) - Earth Release: Hiding in Rock Technique
Rank: B
Type: Defence/Supplementary
Range: Long
Chakra Cost: 30
Damage Points: N/A
Description: This is a technique that allows its user to blend into rocks and then move in and out of other rocks undetected.
Note: Can only blend through on B rank and below Earth Techniques
Since the fire and wind wouldnt immediately cancel out you wouldnt be able to notice and when it did start to clear up you'd see Broly exactly as he was, making handseals in preperations for another jutsu. However this is only a decoy and as you jump back, before you can finish your handseals, Broly silently emerges from the ground just behind you and silently stabs you in the neck with a kunai before you can even realize what happens. This of course ends your life.
(Muon Satsujin Jutsu) - Silent Homicide Technique
Rank: D
Type:Attack
Range:Short-Mid
Chakra Cost:10
Damage Points:20
Description: Muon Satsujin Jutsu, the ability to commit a silent homicide, is a technique to dispatch your foe with no warning. Your quick speed and skills will instantly kill them before they can provide a defense.
Tactic:Best used with Hidden Mist jutsu.