In the Starstrike series, the Zeo-Turbo transition gap is a set of events that occurred between the canon Zeo finale and the canon Turbo show.
Before the Turbo movie
Having temporarily destroyed the Machine royal family, Rita and Zedd return to the moon. They begin construction of a prototype of an improved Serpentera; it is smaller than the original, but much more agile. They get close to finishing it, but it lacks a power source.
In the meantime, some cogs on the Machine Empire's base are rebuilding Mondo. With all of the villains so occupied, the Rangers enjoy a time of peace. Zordon warns them that the Empire is not gone for good, but believes that they can rest for a while.
When he's ready, Mondo goes after Zedd and Rita again. Zedd realizes that their palace will be destroyed for real this time. He pushes a button that floods the Serpentera prototype's hangar with moon-dirt so that it cannot be found. He hopes to come back and get it at some point. He and Rita escape the moon again, with Finster, Goldar and some Tengas, but the rest of their crew is destroyed. They seek out the United Alliance of Evil to complain about Mondo's monopoly on galactic domination.
Mondo begins a full-scale invasion of Earth, bringing thousands of Cogs and Quadrafighters. He destroys some buildings to demonstrate his firepower. The Zeozords face him and are destroyed. Mondo gloats that if he didn't have enough firepower already, Serpentera is waiting for him on the moon, so the Rangers should just give up. Rocky gets really spooked by this experience, fearing that they will not be able to protect the Earth this time.
The Rangers regroup and form a plan. Zordon notices that Mondo's palace is relatively empty, as his focus is on Earth. The Rangers take the space-capable Super Zeozords to Mondo's palace, as secretly as they can. They blast their way in and destroy all the machinery in sight. Eventually they damage a central computer that gives instructions to all of the Cogs. This renders most of Mondo's firepower useless, not only on Earth but everywhere else he has conquered. They then return to Earth and destroy Mondo again.
After the Turbo movie
The active Rangers tell Jason about what happened with Mondo after he left. He finds Mondo's mention of Serpentera to be particularly odd.
Bulk and Skull return from France to Angel Grove.