using two shaders together

Hi. I created my own vertex shader that manipulates the vertex position with a function of two variables. I attached it to a material and placed it as the second material on the object that already has the default-diffuse material. The result is this criss-cross of color that shifts as the camera move.

What should I do? can i “direct” the fragment part of my shader to be the diffuse one? is there a way i can “turn off” my fragment shader so there won’t be two active ones?

Here is the shader:

Shader “Custom/ShockwaveShader” {
Properties {
_TimeFromExp(“TimeSinceExplosion”, float) = 1
_ExplosionPos(“ExplosionPosition”, Vector) = (0,0,0)
}

SubShader {
	Pass {

	CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag
	#include "UnityCG.cginc"
	
	float _TimeFromExp;
	float4 _ExplosionPos;
	
	struct v2f {
		float4 pos: SV_POSITION;
		float3 color: COLOR0;
	};
	
	float dist(float3 a, float3 b) {
		return sqrt( (a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y) + (a.z - b.z)*(a.z - b.z) );
	}
	
	v2f vert (appdata_full v)
	{
		v2f o;
		float dis = dist(v.vertex, _ExplosionPos);
		float4 norm = normalize(v.vertex - _ExplosionPos);
		float funcVal = exp(-pow((dis/5 - _TimeFromExp),2));
		float4 ver = v.vertex + norm*funcVal;
		
		o.pos = mul(UNITY_MATRIX_MVP, ver);
		
		o.color = v.color;
		return o;
	}
	
	half4 frag (v2f i) : COLOR
	{
		return half4(i.color, 1);
	}

	ENDCG
	
	}
}
Fallback "VertexLit"

}

I think you should only be using one material at a time for the same uv mapped space. If you need a diffuse texture just add it to your shockwave shader and diable/remove the default diffuse shader.