Disclaimer: It’s not as bad as it looks, the springs are not under tension.
Still: Don’t do such stuff. Even if it’s save you will look stupid. People will make fun of you and/or tell you not to to it. This is especially fun in a shared workshop. Back to the point: Putting spanners only on one side of the spring (which is under tension) is guaranteed to make funny bouncy spring make funny bouncy stuff in the workshop an maybe hurt/kill somebody. Not funny.
The save way to go is to use proper spanners, compress the spring, remove it and then decompress it. And we also have decent spanners in the shop you don’t have to use the cheapos… If you have to support something which is under pressure please do it right. Use something which has a proper stand (three or more legs) so it won’t jump away easily if somebody kicks it unintentionally. Also use a layer of wood to distribute the load.
In this case I would have used the workshop pushcart (you can see the wheels in the back of the photo) and put it under the differential or some proper three legged stands…