This question has been already answered here : How to remove toolbar buttons in Autodesk Forge Viewer version 7
To complete Bryan's answer with the buttons you want to hide, here's a few more class
names you can use :
.adsk-viewing-viewer #toolbar-modelStructureTool{display:none!important}
.adsk-viewing-viewer #toolbar-explodeTool{display:none!important}
.adsk-viewing-viewer #toolbar-measurementSubmenuTool{display:none!important}
.adsk-viewing-viewer #toolbar-orbitTools{display:none!important}
.adsk-viewing-viewer #toolbar-panTool{display:none!important}
.adsk-viewing-viewer #toolbar-zoomTool{display:none!important}
.adsk-viewing-viewer #toolbar-bimWalkTool{display:none!important}
.adsk-viewing-viewer #toolbar-cameraSubmenuTool{display:none!important}
Using your browser inspector you can easily find these class
names in the html .