It’s great you are still thinking about it.
A well bonded and character compatible pair will display normal dominance - that’s it! It is an essential way of maintaining their relationship. It’s quite simply normal piggy behaviour and nothing of any concern, if anything it’s a joy to see such behaviours!
If there is any squabbling, think of it as kind of like children - ‘mum, he’s looking at me’ kind of bickering with absolutely no malice in it whatsoever.
No, a bond does not just suddenly break for no reason at all.
A bond will only fail from the beginning if they are not character compatible and break if there are underlying, unresolved tensions or issues which come to the surface. This is why getting the right friend is important to ensure it doesn’t happen.
Things such as medical separations can break bonds but that isn’t an issue because if you know that, quite simply you don’t ever medically separate them!
With that said, even if a bond did break, two piggies are better off living side by side than for a piggy to never have any companionship and be kept completely alone without even a neighbour.
Environment changes - some pairs, boar pairs in particular, are more sensitive to environment changes than others. Again, you are able to mitigate this by always cleaning half the cage on one day and then the other half the next day. What you don’t want is to completely remove all scent from their normal environment.
If you use fleece, then quite simply rubbing the soiled fleece onto the new fleece on clean out day will suffice in transferring scent to the new bedding.
Veggie hogging - veggies aren’t the main diet so provided there are lots of hay piles around the cage then both pigs get plenty to eat.
If you follow the advice of scatter feeding veg and pellets into hay piles around the cage then that prevents food hogging because the dominant quite simply cannot be everywhere at once. It is also excellent mental stimulation.
If it was to happen that one pig was just much faster at eating than the other and you could consistently see one pig just wasn’t getting much (this isn’t food hogging and is probably, should one get more than the other, be the main reason rather than actual territorial behaviours over food) then you quite simply you can hand feed the veg to the pigs to ensure each gets their share - it’s also a lovely bonding time for you.
I will be honest, I have never given a thought to one of my pigs getting more veg than the other - if it happens then it doesn’t matter - the other usually get more the next day. It isn’t something I monitor - I just throw the veg in, check they are eating it and go about whatever else I need to get done. Their weight checks are telling me about their hay intake and that is the most important factor.
Cage size is one of your main considerations - you need to provide 180x60cm for a boar pair or 150x60cm for a boar/sow pair (if I remember rightly, zorro is neutered soma sow is an option), along with multiple of every item in the cage. Ensure all hides have two exits so it doesn’t risk one piggy getting trapped by the other.
As zorro has spent all his life alone, he hasn’t had the socialisation he needed at the right time in his life to learn hierarchy and society. Its not a reason to not get him a friend, but you need to go about bonding carefully to ensure he doesn’t overreact (which is usually through fear than aggression). It’s things like ensuring they are kept side by side for probably a lot longer than one normally would before you even attempt the bonding on neutral territory. This would enable him to get used to seeing another piggy before being put in a position of sharing territory with one another.
I will add that none of these things are a reason to not get a friend for zorro. Even if a bond did break, he would still be better off with a broken bond and a neighbour than he is now without another piggy at all.
If you can get to a rescue centre to find him a new friend then that is the best way to go about it. They will be able to support in finding the right friend for him.
The guides below explain everything in much more detail
- What can trigger a new hierarchy sort-out?
- What can I do to mitigate the impact?
With an average life span of only around 3 years and a hostile environment, wild guinea pig social life is much more fluid and eventful, whether that is losses, births, regular leadership changes, new boars being accepted or changes to the territory due to climate extremes, infectious illnesses, predation and the waxing and waning of group fortunes and the amount of territory they can claim around their denning areas.
What can trigger...
Introduction
1 A Look at Social Identity
- Identity and Self-awareness
- Herd and Group: Juggling social identities
2 Herd Behaviours
- On the move
- Shared herd feeding
3 The Group and I
- Group identity vs. individual identity
- Group establishment and affirmation
- Use of the denning...
1 Depression
- Acute Pining
- Loneliness
2 Bullying
3 Hormones and Aggression
- Boars: the teenage months
- Sows: ovarian cysts
4 Fear and Stress
- Prey animal default setting
- Fear-aggression
5 Antisocial and disabled guinea pigs
This text is part of...
1 Common myths and misconceptions
2 The different ages (including teenage)
- Important biological facts
- The formative 'School Weeks' (3 weeks - ca. 4 months)
- The Teenage Months (ca. 4-14 months)
- The Adult Years (ca. 15 months - ca. 4-5 years)
- The Golden Age (ca. 4-5 years until end of life)
3 What do boars need? (List of boar dos and don'ts)
- Space, space and more space!
- Respecting the hierarchy
- The 'one for each...
Introduction
1 When is a 'single' really a single?
- Bought singles
- Fallen-out and aggressive piggies
- Bereaved guinea pigs
- No interest in other guinea pigs
- Disabled and special needs guinea pigs
2 Companionship options (with pros and cons)
- Dating
- De-sexing (neutering or spaying)
- Living alongside
- Buying a baby companion
3 Caring for single guinea...
rarely things can go wrong, so it’s good to have a plan B in place, but if you follow the guidelines and ask for help here then it’s very unlikely you’ll need it. You’ll also find your piggies perk up and bring you a lot more entertainment and happiness - and it’s much better for them to have company, as I’m sure you know and it’s good you’re doing your research and thinking it through carefully 
