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Like Zac and Eric mentioned: try subdividing the mesh and see if there's any smoothing errors like pinching, stretching, or unintended surface deformation. The unsubdivided wireframe is great for clarity but it's easier to identify specific problems by comparing it to the smoothed mesh and subdivision wireframe preview.

As far as the topology routing strategy goes, it really depends on what the model will be used for, but it's worth mentioning that a couple of posts up there's a conversation that about topology routing around a complex shape intersection and the answer there is probably applicable here too.

It's really easy to get bogged down moving loops around without seeing a lot of progress. Which is why it's generally considered best practice to block out all of the major forms first then solve any basic topology flow issues during the block out, before adding a lot of support loops. This way the shapes themselves and the existing geometry in those shapes will help guide the loop flow around the shapes.

Here's some links to other write-ups that cover how to streamline the block out process and solve topology flow issues so most of the final support loops can be added with a few simple bevel / chamfer operations.

Below is an example of what this approach could look like for this part of the model: Start by blocking out the larger curved shapes and the bulk of the complex form underneath, maintaining a few key loop paths off the curved shapes. Try to use the existing geometry in the curved shapes as part of the loop flow path for the support loops whenever possible.

This is typically done by adjusting the density of the curved surfaces and the placement of intersecting geometry so the shape transition lands between the existing segments of the curved surfaces.  That way the intersecting shape and the support loops around it are less likely to disrupt the segment spacing of the existing shape, avoiding unintended surface deformation.

Continue blocking out the secondary forms then join the two shapes together. Direct the loop flow around the combined shapes to define the basic loop flow around the shape transitions and any tertiary details. Sometimes it's easier to work from the outer most bounds of the shapes and push recessed areas inwards and other times it's easier to work from the inner most bounds of the shape and extrude the details outwards.

On this particular shape it seemed to be easier modeling inwards. So the basic loop path was created where it intersects the hemispherical shape then the lower section was pushed inwards to create the depth along that curved lip. Which avoids potential deformation issues on the back of the hemispheres.

Add the basic loop paths around the shapes once all of the major forms are accurately represented. Keeping things relatively simple at this stage makes it easier to solve a lot of basic topology flow issues and the loop paths established here will both hold the larger curves and provide a path for the final edge support loops that are added later.

With the basic loop routing supporting the larger shapes and providing a path for the support loops around the shapes, simply select the edges that define the outer profiles of the shapes and shape transitions then add the support loops with a bevel / chamfer operation. This process can be further streamlined using a bevel / chamfer modifier that's controlled by edge weights.

The example below highlights how the edge support loops created by the bevel / chamfer operation automatically resolve the problems with the corner intersections with a combination of grid and diamond quad topology.  Here's some links to additional write-ups that cover a few different ways to approach these kinds of corner intersections using both grid and diamond quad topology.

 
https://polycount.com/discussion/comment/2718563/#Comment_2718563

Below is what the final model looks like. All of the smaller support loops, along the edges that define the shapes, are automatically generated using a bevel / chamfer modifier that's controlled by edge weights.

Most of the topology flow issues were solved early in the block out: the few support loops for the larger forms constrain all of the triangles and n-gons to flat surfaces between the edge support loops where they can't cause any unintended surface deformation. Which is why the mesh subdivides cleanly without being all quads.

Recap: Keep things relatively simple and block out all of the larger forms. Use the block out process to solve most of the topology routing issues before adding a lot of complex support loops. Try to use the existing geometry of curved surfaces as part of the support loop structure around complex shape intersections. Streamline the modeling process by adding final edge support loops around shape using a bevel / chamfer operation.

Some other topology write-ups that may be helpful on this project:

A partially automated or at least semi-non-destructive alternative to modifiers is using a plug-in or add-on that enables re-working existing round overs and automatically creates fillets around boolean operations when poly modeling. As impressive as those types of tools are, especially for concept modeling, whether or not the final model is bake ready really just depends on how the tool set was used and what the overall workflow looks like.

All that said: basic subdivision modeling is fairly straightforward and there's a couple of different ways to approach creating a base mesh that allows the subdivision to do most of the smoothing work.

Okidoki demonstrated the basics of an edge extrusion approach in the previous post. Another option would be to use a strip modeling approach. That way it's a bit easier to solve some of the shapes without having to worry about potential topology flow issues before joining all the surfaces together.

Once all of the primary and secondary forms are accurately represented and the segments are more or less lined up, fill in the missing faces or merge down the adjacent vertices to close the mesh. Resolve the topology to all quads by dissolving or redirecting the loops around the shapes as required.

Try to minimize any unwanted shape deformation or abrupt changes in segment spacing. (Slide the geometry along the surface and relax the mesh as needed to maintain the curvature of the underlying surfaces.) If smaller tertiary details need additional geometry then finalize the larger shapes and apply a subdivision level before adding the details.

Here's what the final base mesh could look like, before adding any of the recessed cut outs like the internal shell holder.

A couple of pages back there's a longer write-up about blocking out stocks. It covers how to create the basic shapes, when to apply subdivision during the block out, and how to redirect the loop flow around secondary and tertiary details: https://polycount.com/discussion/comment/2801011/#Comment_2801011

Recap: Keep things relatively consistent. Block out he larger forms first. Focus on creating accurate shapes then let those shapes guide the topology flow around them. Work in stages and apply subdivision levels as required to support smaller details on complex curves. Let the subdivision handle most of the smoothing.