I have a course in spanish and english where I cover all the process of this kind of work, if you're interesting on it you can check here: https://www.domestika.org/es/courses/608-diseno-y-modelado-de-una-nave-sci-fi-en-3d/juannovelletto
I did this tank in my free time. The inspiration was the Fulgora laternaria, a winged insect, but with the iterations the shape was changing.
In the process, I worked with 3dcoat at first, for the sketch, and then I did the blockmesh with maya and zmodeler. For the cannon I worked with 3DCoat again, and the exported to ZBrush for did more details withs alphas. Finally I did the renders in Keyshot and added some FX in Photoshop.
I hope you like it!