I used to get my smoothies at Jamba Juice... all jokes aside, for a smoother transition you can try a morph with your radial zoom on top.
Here's a simple morph method using stock AE plugins only:
Use Mesh Warp.
Set 2 layers in a AE comp- the "morph from" layer on top of the "morph to" layer.
Start on the layer you want to morph from- apply Mesh Warp and set keyframe. Move 8 to 15 frames (or as many as you need your morph to be) and change transparency to 50% so that you can see the layer under. Use the mesh warp to distort the features of the top layer to match those of the bottom layer.
Apply Mesh Warp to bottom layer and set keyframe at the end of the transition. Go back to the beginning of the transition and use the Mesh Warp to distort the bottom layer to match the top one's features.
Set transparency keyframes to animate the top layers opacity from 100% to 0 for the length of the morph.
That's basically it.