I am not familiar with any Zizzle games... but you have General Illumination(GI) which is above the playfield and Controlled(insert) illumination located below the playfield. To get underneath, you need to remove the lockdown bar and slide the glass out then lift he playfield. It's as simple as swapping the incadencents with the same socket type of LED's(#44 bayonet base/#555 wedge base). The GI bulbs can be reached by taking off the plastics above them, or sometimes you can unscrew the socket from underneath with a 1/4" bit. Again, not sure how a Zizzle is built. I order Non Ghosted frosted LEDs from Pinball life. All up to you on color. Most choose between cool or warm white.

Stet my above comment. Looks like Zizzle is completely different. The advice given in the thread Schamattack posted above is more accurate for your machine. Good luck on it!