Hello again meh! Pet lambs will not need worming often, especially if you are keeping them on land not previously used for livestock esp sheep. Commercial farmers in the past have wormed frequently, even as often as 6 weeks, more often 3 monthly, then they would move them on to fresh ground. With the arrival of wormer resistance, this practice has increased resistance greatly - if you move your sheep onto clean ground after worming then only the resistant worms will survive and without competition from the non-resistant worms they will increase in numbers enormously. So it has been realised that it is best to move them onto 'dirty' ground so that the resistant worms at least have some competition.
I think Zolvix is meant to be, or should be, used only in flocks where there is known anthelmintic (wormer) resistance, to knock those worms out in a blitz attack. If everyone uses it then we will soon be searching for yet another type of wormer, and Zolvix has taken years to develop.
For worming your lambs, learn to 'read' their general health and condition before dosing them up. A wormy lamb will look thin and peaky, not in the prime of health or thriving and may well have scours (diarrhoea). That is the time to worm - or slightly before that when there is the first hint that all is not well. Use a gentle wormer such as Panacur. You might only need to worm them again once in the Autumn then annually after that, unless you have brought in wormer resistance with them.
Rosemary, it could be worth you using Zolvix before you move your sheep if the ground you are moving to is clean but you have resistance to wormers already in your flock.